The structure of foreign policy attitudes in transatlantic perspective: Comparing the United States, United Kingdom, France and Germany

. While public opinion about foreign policy has been studied extensively in the United States, there is less systematic research of foreign policy opinions in other countries. Given that public opinion about international affairs affects who gets elected in democracies and then constrains the foreign policies available to leaders once elected, both comparative politics and international relations scholarship benefit from more systematic investigation of foreign policy attitudes outside the United States.Using new data,this article presents a common set of core constructs structuring both American and European attitudes about foreign policy. Surveys conducted in four countries (the United States, the United Kingdom, France and Germany)provideanexpandedsetofforeignpolicy-relatedsurveyitemsthatareanalysedusingexploratory structural equation modeling (ESEM). Measurement equivalence is specifically tested and a common four-factor structure that fits the data in all four countries is found.Consequently,valid,direct comparisons of the foreign policy preferences of four world powers are made. In the process, the four-factor model confirms and expands previous work on the structure of foreign policy attitudes. The article also demonstrates the capability of ESEM in testing the dimensionality and cross-national equivalence of social science concepts.


Introduction
Foreign policy is an important part of what governments do, yet surprisingly little research compares public attitudes about international affairs across countries. The question of what the public thinks about foreign policy has been studied extensively in the United States. Still, there remain unresolved questions concerning foreign policy opinions in other countries. We contribute to both the study of comparative politics and international relations by asking a simple question: Do the core constructs structuring American attitudes about foreign policy translate well to the mass publics of key European powers? Using data from the United States, United Kingdom, France and Germany, we identify a structure of foreign policy attitudes that fits opinion data in all four countries.
The questions of what Americans think about foreign policy and how they structure their views of foreign affairs has occupied analysts of foreign policy and political behaviour for more than five decades. The earliest attempts to answer this question concluded that there was little to discuss: Americans paid little attention to politics 'beyond water's edge' (Almond 1960;Converse 1964). This view was eventually replaced by work from Wittkopf (1990Wittkopf ( , 1994 and Holsti and Rosenau (1986, 1988, 1990) that identified opinion as structured by two distinct forms of internationalism, typically described as 'militant internationalism' (MI) and 'cooperative internationalism' (CI) This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
repeatedly been found, some work has found empirical support for additional attitudinal dimensions (Chittick et al. 1995;Kertzer et al. 2014;Rathbun et al. 2016;Richman et al. 1997). Although the exact number and content of dimensions in any factor-analytic model is (in part) subject to the number and the content of indicators used, the question of crossnational similarity of foreign policy constructs nevertheless remains unresolved. When using identical items across nations, how similar or different would the structures look?
Foreign policy attitudes are important because there is strong evidence for an electoral connection between public opinion and foreign policy (Aldrich et al. 2006). When political office is at stake, politicians take notice (Cain et al. 1979;Fenno 1978;Mayhew 1974). At the most basic level, foreign policy attitudes matter because they help shape how parties and candidates are evaluated as well as who holds office (Aldrich et al. 2006;Baum & Potter 2008;Gravelle et al. 2014;Soroka 2003). In addition to the direct effect of a country's public opinion on making foreign policy, governments and leaders are possibly advantaged when they also understand the domestic public opinion environment in other countries and the constraints their counterparts face.
Despite its substantive importance, the literature on public opinion toward foreign policy remains marked by certain shortcomings. First, much of the literature relies exclusively on studies of American public opinion, or the comparison of American attitudes with those of a single nation (Bjereld & Ekengren 1999;Hurwitz et al. 1993;Jenkins-Smith et al. 2004). Inferences about the content of foreign policy attitudes among mass publics writ large are obviously more tenuous when the bulk of the evidence derives from a single public. Second, many existing cross-national analyses of foreign public opinion focus on specific issuesfor example, joining the American-led coalition invading Iraq in 2003 (Kritzinger 2003), a cooperative environmental agreement (Brechin 2003) or nuclear weapons and power (Jenkins-Smith et al. 2004). 1 Just as focusing on a single country limits the generalisability of results, so too does focusing on a limited set of specific policy issues.
Following the terminology of Hurwitz and Peffley (1987), our analyses reveal the outlooks or 'postures' that citizens possess that inform their view of how their nation should behave in the international arena. These broad postures are in many respects more important than attitudes on specific issues, which change over time. It is these postures that shape views on the specific foreign policy issues of the day (Hurwitz & Peffley 1987). Crossnational comparisons of foreign policy postures may illuminate similarities and differences in the constraints leaders face when foreign policy crises emerge. Drawing valid comparisons, however, requires careful attention to measurement and equivalence, which is a central feature of our analyses.
In this article, we bring new data to bear on two important questions: (1) how do mass publics structure their attitudes toward foreign affairs; and (2) how similar or different are these structures across our four cases? The answers we provide are novel in two respects. First, we argue that there are important concepts distinct from militant internationalism and cooperative internationalism in publics' collective minds. The MI/CI framework has endured for a reason, but it is reasonable to assess whether these two dimensions offer a complete account of foreign policy preferences. To be clear, we find unambiguous support confirming the existence of both militant and cooperative internationalisms. We also find remarkably similar structure across all four countries, but the empirical evidence makes it abundantly clear that the MI and CI dimensions tell an incomplete story about foreign policy attitudes.
We thus argue for a more multifaceted (and multifactor) view of how mass publics structure their attitudes toward international politics.
So, what dimensions help complete the picture? We find two. In accord with other recent scholarship (Kertzer 2013;Rathbun 2007), we find an isolationist posture that is distinct from MI and CI. This finding is important because it means that isolationism is not simply the joint negation of the latter two concepts (Braumoeller 2010;Urbatsch 2010). Further, our data reveal that 'liberal internationalism' (often used synonymously with cooperative internationalism) may be better explained as two separate (but related) constructs. One captures support for international institutions and cooperation -and deserves to retain the name cooperative internationalism. The second 'liberal internationalism' dimension reflects support for redistributive policies like foreign aid -and perhaps reflects attitudes toward global justice.
Our second novel contribution is a direct assessment of the cross-national equivalence of foreign policy attitude constructs. As noted by King et al. (2004), the cross-national equivalence of survey-based attitudinal measures often is assumed rather than tested explicitly in comparative research. Recent research has thus sought to test the cross-national (or cross-group) measurement equivalence (or measurement invariance) of various key concepts in political science, such as democracy (Ariely & Davidov 2011), the welfare state (Stegmueller 2011), and national identity (Davidov 2008. We are similarly motivated to evaluate whether broad attitudes toward foreign policy are structured equivalently on either side of the North Atlantic. Finding measurement equivalence greatly simplifies comparison of foreign policy attitudes across advanced democracies. We structure the article as follows. First, we briefly review the literature on foreign policy attitudes while pointing out some of its limitations. Second, we introduce the American, British, French and German survey data that underpin our empirical analyses. Third, we motivate the statistical methods we employ -namely exploratory structural equation modeling (ESEM) (Asparouhov & Muthén 2009) -as a means to evaluate factor structure and measurement equivalence (or measurement invariance) across the four countries studied. Fourth, we describe the results of the data analysis for the four countries, drawing attention to both the similarity in the structure of attitudes across the different country contexts examined while also noting differences in country-level factor scores. We conclude by noting areas for future research.

The structure of foreign policy attitudes: Competing approaches
The earliest influential model of the structure of foreign policy attitudes argued that there was in fact very little structure to speak of underlying mass public opinion on foreign policy (Almond 1960;Converse 1964). This view was gradually replaced by studies of American public opinion from the 1950s to the 1970s claiming that the public held a relatively coherent set of attitudes relating to engagement with the world, both militarily and economically, and were seen as falling somewhere on a single internationalist-isolationist continuum (e.g., McClosky 1967;Russett 1960;Sniderman & Citrin 1971).
This view of a single internationalism-isolationism dimension came to be replaced in the 1980s as a result of a series of seminal publications by Wittkopf, whose central argument was that in the wake of the Vietnam War, American public opinion became bifurcated on foreign policy issues. The issue was no longer whether but how the United States ought to engage with the world. Wittkopf (1981) relied on factor analyses of survey data collected by the Chicago Council on Foreign Relations (CCFR) to advance the view that 'two faces' of internationalism characterised American public opinion toward foreign policy: attitudes toward the use of the military abroad ('militant internationalism') and attitudes toward nonmilitary engagement ('cooperative internationalism').
Wittkopf subsequently reproduced the two-factor MI/CI model using different data (Wittkopf 1986(Wittkopf , 1990(Wittkopf , 1994Wittkopf & Maggiotto 1982). The same factor structure was observed in samples of elites, implying that elites structure their views in the same manner as the public, though this was not to say that elites' foreign policy beliefs exhibited the same distribution (Holsti & Rosenau 1986, 1990Wittkopf & Maggiotto 1983). Similar factor structures were also obtained outside the American context in other industrialised states, including the United Kingdom (Reifler et al. 2011) and Sweden (Bjereld & Ekengren 1999).
In contrast to the 'horizontal' organisation of Wittkopf's two factors, Hurwitz and Peffley (1987) advanced a model of 'vertical' constraint whereby more specific policy attitudes are structured (or 'constrained') by broader foreign policy postures, which are in turn structured by yet broader core political values. Recent work has reconfirmed the insight that core values inform policy preferences, while also demonstrating the status of isolationist sentiment as a factor distinct from different forms of internationalism (Kertzer 2013;Rathbun et al. 2016). This recent work has 'squared the circle', bringing together core insights of Wittkopf and others with those of Hurwitz and Peffley: the basic MI/CI framework serves as a useful account of foreign policy postures informed by underlying core values. Consequently, the Wittkopf-Holsti and Rosenau MI/CI framework retains its primacy in the foreign policy attitudes literature. Indeed, it has been described as the 'gold standard' of models of foreign policy attitudes (Nincic & Ramos 2010: 122). 2 This, however, raises two questions. First, while there is a general persistence of MI and CI factors, are these the only regularly observed factors? And second, should the MI/CI framework be seen as the gold standard theoretical account of American attitudes, or for foreign policy attitudes more broadly?

Data
To answer these questions, we draw on original survey data collected in the United States, the United Kingdom, France and Germany. Country case selection was motivated by the fact that these four countries are the top four Western democracies in the amount of money spent on national defence. All four have the economic and military resources to be active in world affairs. As NATO members, they also have similar security concerns and commitments. At the same time, there is variation in their political institutions: the United States is a presidential system, France is a semi-presidential one, and the United Kingdom and Germany are parliamentary democracies. While such institutional differences are not our primary concern, it is important to note that more direct comparisons of attitudes at the mass level may help isolate the effect of institutions on observed foreign policy differences. There are also notable differences in national experiences in war and conflict. France, the United Kingdom and the United States share significant experiences in counter-insurgency campaigns, some of which have incurred substantial casualties and substantial domestic opposition. German strategic culture, perhaps in response to defeats in the First and Second World Wars, eschews high-intensity combat (Rynning 2003). How these different legacies shape foreign policy attitudes is an important question that we hope future research will address.
In approaching the design of these original surveys, our intent was to design instruments that would allow for the possibility of complex, multidimensional structures that varied significantly across countries. More specifically, we included multiple questions designed to capture each of the following potentially distinct attitudes about international affairs: militarism, multilateralism, isolationism, unilateralism, humanitarianism, egalitarianism and pacifism. 3 After preliminary analyses, we identified 14 indicators for analysis with at least one item from each of the concepts other than pacifism. Our expectations were informed by prior work identifying separate dimensions that capture attitudes about the exercise of military power, on the one hand, and cooperative engagement with other states and intergovernmental organisations, on the other (Mader 2015;Reifler et al. 2011;Wittkopf 1986). While some attitudinal models (e.g., that of Wittkopf) see isolationism as the absence of military and non-military engagement, recent empirical research identifies an isolationism factor distinct from the other two factors (Kertzer 2013;Rathbun 2007). Isolationist thought is conventionally viewed as an American affliction, though segments of the public in many democratic states express an aversion toward involvement beyond their borders (e.g., Mader & Pötzschke 2014).
While the concepts of 'militant internationalism', 'cooperative internationalism' and 'isolationism' are well-established, some of our other concepts may require more explanation. One might believe that cooperation is desirable, but their country needs to be willing and able to act alone if the situation warrants such action. This sentiment of unilateralism is important to probe in light of periodic unilateral actions by the United States (Skidmore 2005). In addition to the United States, France has a history of acting distinctlymost prominently with its (temporary) withdrawal from NATO in the 1960s. Large segments of the British public and their elected politicians also express a desire for Britain to engage with the outside world in ways that differ from prevailing policy-making consensus (e.g., with Brexit). Only in Germany does unilateralist thought appear muted. Given the economic crisis and the German position within the Eurozone, this too may change (see Le Gloannec 2004). The fact that circumstances surrounding the use of force or the exercise of economic statecraft may bear on public views of unilateralism in foreign policy underscore the need for its cross-national validation.
Finally, there is a renewed emphasis on the need for developed nations to help the world's poor through foreign aid. The UN Millennium Project's benchmark of at least 0.7 per cent of Gross National Income (GNI) spent on overseas assistance regularly makes headlines. We included four potential global justice indicators that represent both humanitarian and egalitarian constructs (as per Feldman & Steenbergen 2001) that we think capture public support for more redistributive international policies.
Survey data collection was undertaken by YouGov in November 2011 in the United States and United Kingdom, in May 2014 in France and in October 2014 in Germany. YouGov's approach to survey sampling involves using a matching algorithm designed to draw online samples from opt-in panels that approximate probability samples (Rivers 2006). Selected respondents are matched on demographic factors (gender, age, education and Tables 1 and 2 delineate the indicators by hypothesised postures and the percentage answering 'agree' or 'strongly agree' to each statement. (The full distributions appear in the Online Appendix). A number of similarities and differences emerge from these tables. Responses to the hypothesised militarism indicators suggest that the German public is much less inclined toward maintaining and displaying a readiness to use military force than their French, British and American counterparts. A majority of French and British respondents view maintaining a tough posture as important, while Americans and Germans seem more willing to listen before acting. Respondents in all countries, however, are amenable to diplomatic solutions to crises before going to war. Responses to the three indicators we hypothesise to be reflective of CI provide varied results. One curiosity is that members of the American public are most receptive to the idea that their country should consider views of allies. At the same time, Americans and the French appear more critical when asked about working through the United Nations or when asked about building a broader consensus (without the mention of allies). The crossnational variation in response patterns to the proposed CI indicators validates the decision to use multiple indicators for a given foreign policy posture.
The French public stands out in its level of agreement with the three proposed isolationism indicators. A majority of French respondents agree that international involvement is not worth it if the well-being and happiness of the citizenry are sacrificed. A plurality of French respondents also expressed agreement when presented with statements asking whether it is best for nations to 'stay out' and/or 'avoid involvement' in foreign relations. Americans and Britons are much more inclined toward engagement than the French, with Germans taking a middle ground.
As for willingness to act unilaterally, Britons stand out as most apt to wish to do things their own way. These questions may tap into British ambivalence toward the European Union and/or regret following America into Iraq. Germans are second only to the British in wanting to chart their own course or 'go at it alone', but are not as prone as Americans and the French to believing they are getting pushed around by international organisations.
Responses to the last set of indicators show that there is little support for wealth redistribution across borders. Close to 1 in 4 German respondents and 1 in 5 French respondents express willingness to share their country's wealth with others, but just over 1 in 10 Americans and Britons express the same opinion. Majorities of the British, American and French publics agree that their country does 'enough to help the world's poor', as does a plurality of the German public.

Methods
Given the two linked goals of our research -the dimensionality of foreign policy attitudes among mass publics and the cross-national equivalence of these dimensions -we analyse a series of exploratory structural equation models (ESEMs). ESEM is an extension of exploratory factor analysis (EFA), confirmatory factor analysis (CFA) and structural equation modeling (SEM) (Asparouhov & Muthén 2009;Marsh et al. 2014). Factors in ESEM are analogous to those in EFA in that all items are allowed to load on all factors; this is appropriate when expectations regarding the factor structure (i.e., the number of factors and which items ought to be associated with which factors) are not given by existing theory. ESEM thus represents a relaxation of the assumption of 'simple structure' (items loading on only one factor, and no cross-loadings) typically characteristic of applications of CFA, and one that is 'more closely aligned with reality, reflecting more limited measurement knowledge of the researcher or a more complex measurement structure' (Asparouhov & Muthén 2009: 399). ESEM also allows for factor loadings, means and intercepts to be alternatively constrained to be equal or free to vary -all features of CFA and SEM.
In ESEM, the question of how many factors underlie a set of data is framed in terms of the minimum number of factors necessary to achieve good overall fit to the data. This involves testing alternative models (e.g., one-, two-, three-, four-factor models and so on) against the same data and evaluating them on the basis of overall model fit using the fit indices commonly used in SEM (Preacher et al. 2013). By emphasising the minimum number of factors to achieve good fit, the model selection approach seeks to strike a balance between not overfitting the data at hand while also not ignoring important complexity and nuance -that is, specifying a model structure that is no more complex than necessary and is amenable to cross-validation using different data (Cudeck & Henly 1991;Preacher et al. 2013).
To be clear, we care more about the content of the factors than their exact number. Still, determining the appropriate number of factors is an essential step in understanding what the data reveal about the content and structure of foreign policy thinking in these four countries. To determine the correct number of factors, we test a series of ESEMs with 1-5 factors in three separate sets of analyses: in each country separately, with a pooled dataset with all four countries while allowing factor loadings and item thresholds to vary across countries (representing configural equivalence, described below), and again with a fourcountry pooled dataset constraining factor loadings and thresholds to be equal across all four countries (representing scalar equivalence, also described below). The goal of these analyses is to find the minimum number of factors that describe the dimensionality of the data. Once the number of factors is ascertained, we then turn to the question of their equivalence across countries.
In assessing cross-national equivalence/invariance, the literature on cross-national comparisons distinguishes between different, progressively more stringent levels of equivalence. Those relevant to our analyses are configural equivalence and scalar equivalence. Configural equivalence requires only that 'factor structures are equal across groups: The same configurations of salient and non-salient factor loadings should be found in all groups' (Davidov et al. 2014). Furthermore, no constraints are imposed on the factor loadings: they are allowed to vary across countries (Steenkamp & Baumgartner 1998). In the case of scalar equivalence, the model is further constrained so that item intercepts (or thresholds) are equal across groups, in addition to constraining factor loadings to be equal. Scalar equivalence is necessary for making meaningful comparisons of latent variable means across groups (Davidov et al. 2014;Stegmueller 2011). Scalar equivalence thus indicates that 'cross-national differences in the means of the observed items are due to differences in the means of the underlying construct(s)' (Steenkamp & Baumgartner 1998).

The dimensionality of foreign policy attitudes
Before turning to a discussion of the substantive meaning of the factor structure we identify, we first discuss the process of choosing the appropriate number of factors. In examining models with one through five factors, the results point clearly toward a four-factor model. Separate analyses by country and analyses of the pooled data with specifications for either configural equivalence or scalar equivalence tell the same story (see Table 3). Examining overall model fit, all of the models fit poorly based on the model Chi 2 tests -though experienced latent variable modelers recognise that like all Chi 2 tests, the model Chi 2 statistics are sensitive to sample size and often indicate misfit in large samples (Kline 2015). Given our large sample sizes, we turn to other, more frequently used measures of model fit offered in the SEM literature -in particular the RMSEA fit statistics emphasised by Preacher et al. (2013) in their approach to selecting factor models. 5 Looking at the approximate fit indices for the four-country models, a noteworthy result is the poor model fit for the two-factor models. The RMSEA values of 0.133 for the unconstrained (configural equivalence) model and 0.124 for the constrained (scalar equivalence) model are well above the suggested threshold of 0.08, indicating lack of fit (Browne & Cudeck 1992;Hu & Bentler 1999). Similarly, the two-factor models' values for the comparative fit index (CFI) of 0.847 for the unconstrained model and 0.769 for the constrained model are again well below the threshold of 0.90 for acceptable model fit. Country-specific values of the RMSEA and CFI fit statistics similarly indicate lack of fit. By all of these measures, a two-factor model of foreign policy attitudes fit the data poorly. A more complex model is needed, but exactly how much more complex should it be? Model fit improves appreciably when three-factor models are specified, though they still fail to meet the conventional RMSEA and CFI thresholds for good fit to the data. The CFI of 0.922 for the four-country unconstrained three-factor model is acceptable, but the RMSEA of 0.105 indicates poor fit. With the constrained three-factor model, both the RMSEA (0.090) and CFI (0.883) indicate lack of fit. Acceptable fit is achieved in all four countriesand with the four-country pooled data -only with the specification of a four-factor model. With four factors, the RMSEA and CFI statistics are 0.051 and 0.985, respectively, for the unconstrained model; they are 0.078 and 0.919, respectively, for the constrained model. Similar results are obtained for the country-specific four-factor models. Further, model fit statistics do not improve appreciably with the specification of a five-factor model. This points to a four-factor model as the solution that best represents the structure of foreign policy attitudes in the United States, United Kingdom, France and Germany. 6

The content and cross-national equivalence of foreign policy attitudes
What of the content of these four factors? Examining the factor loadings from the unconstrained four-factor model, there are clear similarities between the four countries (see the Online Appendix). The first factor that emerges in all analyses resembles Wittkopf's and Holsti and Rosenau's cooperative internationalism. This factor centres on support for working through international organisations such as the United Nations, working with allies, the pursuit of global leadership through building international consensus, and an emphasis on diplomacy and the pursuit of peace over the use of force. The second dimension is straightforward isolationist sentiment. Items reflecting ideas such as avoiding involvement with other countries, refusal to risk one's citizens' wellbeing through international entanglements and minding one's own business load strongly on this factor in all four countries. Weaker secondary loadings on this factor are present for the items measuring willingness to disregard international organisations and the views of allies, and agreement with the idea that one's country already does enough to help the world's poor (and by extension, should not do more, or possibly do less). These results reconfirm findings from recent work on foreign policy attitudes that finds that isolationism constitutes a distinct posture in mass public opinion (Kertzer 2013;Rathbun 2007). Isolationism is not equated to jointly scoring low on MI and CI (cf. Wittkopf 1981Wittkopf , 1990. The third dimension (fourth in the United Kingdom) clearly resembles Wittkopf's classic MI factor. This factor centres on the projection of military power abroad, including support for the use of force to prevent aggression and maintaining a strong military. This factor also includes a unilateralist, go-it-alone tendency in the American and French cases, with loadings for items capturing support for disregarding international organisations and allies when interests dictate. These loadings are weaker in the British case, and absent in the German case (these items are more closely tied to the isolationism factor in the United Kingdom and Germany).
The last dimension (third in the United Kingdom) clearly speaks to the redistribution of wealth across borders and improving the condition of the global poor. Items capturing agreement with sharing wealth with other countries and spending significantly more on foreign aid load strongly on this factor, as does disagreement with the idea that one's country does enough to help the world's poor (i.e., a negative loading). In this light, it might reasonably be labeled a 'global justice' factor in that it emphasises global egalitarian aspirations and aligns with the core arguments advanced in the literature on global distributive justice (Beitz 1999;Rawls 1999;Tan 2004).
Overall, the patterns of factor loadings across the four countries are broadly similar, with the conclusion being that the data exhibit (at least) configural equivalence. Not only do four factors emerge from the data, the substantive meaning of each factor is the same in each country context. Still, scalar equivalence needs to be established in order to make direct comparisons of country-level factor means. The answer to this question is provided by the model fit results for the four-country, four-factor constrained model in Table 3. The RMSEA statistic for this model is 0.078, with the 90 per cent confidence interval being 0.076 to 0.079 -just within the conventional range for reasonable model fit -and the CFI statistic is 0.919, again indicating reasonable fit. These results suggest worse fit than the model in which loadings and thresholds are free to vary (RMSEA is 0.051, and CFI is 0.985), but as a more restrictive model where loadings and thresholds are held equal across countries, this is to be expected. It remains the case that model fit does not worsen to the degree that it would lead us to reject the constrained model. The conclusion, then, is that the data exhibit scalar equivalence. The structure of the data in all four countries can thus be represented using the common set of factor loadings presented in Table 4.

The substance of foreign policy attitudes in transatlantic perspective
What, then, can we say about comparisons of the foreign policy attitudes of the American, British, French and German publics in terms of their orientations toward cooperative internationalism, isolationism, militant internationalism and global justice? The answer to this question comes from the factor means from the four-country, four-factor constrained (scalar equivalent) model. Since factor scores have no natural scale, factor score comparisons are made by fixing the factor means for one group (in this case, the United States) to zero and then making pairwise comparisons between other groups and this reference group Stegmueller 2011). These scores provide several findings of note (see Table 5). First, there is little in the way of cross-national differences in CI: there are no significant differences between the United States and either the United Kingdom or France; Germany scores slightly higher than the United States. Interestingly, the United Kingdom, France and Germany score higher on isolationism than the United States. While isolationism has been a recurring theme in the history of American foreign policy (and the study of American foreign policy attitudes), these results indicate that the American public is not, in cross-national perspective, especially isolationist (Braumoeller 2010;Kertzer 2013;Nincic 1997). The United Kingdom, France and Germany also score lower on MI than the United States. The differences between the United Kingdom, France and the United States are modest, while German public opinion is notably anti-militarist compared to the United States -a finding not likely to surprise those familiar with postwar German foreign policy (Berger 1998). Finally, the United Kingdom, France and Germany in turn score progressively higher on the global justice factor than the United States. This finding is interesting in light of the European countries' higher levels of official development assistance as a proportion of GNI, and also in light of previous aggregate-level findings that countries with higher levels of domestic redistribution are generally less favourable toward global redistribution (Noël & Thérien 2002). An explanation for these cross-national differences in mean factor scores may be found in the previously noted differences in political institutions, respective histories of foreign policy, and national strategic cultures. Indeed, such cross-national difference in foreign policy attitudes is a topic requiring further investigation and the development of additional theory.

Discussion and conclusion
Our intention in this article has been to bring new techniques and new data to the decadesold question of how mass publics structure their attitudes toward foreign policy. Drawing on recent survey data from four principal NATO member states -the United States, the United Kingdom, France and Germany -we have argued for a more multifaceted (and multifactor) framework for understanding how publics organise their views of foreign policy. Though the classic MI and CI factors remain important, a rigorous assessment of model fit in analysing series of ESEMs shows that they do not, on their own, adequately describe the patterns in our data. Subsequent scholarship has argued for isolationism as an important distinct concept at the level of mass opinion (Chittick et al. 1995;Kertzer 2013;Rathbun 2007) -an argument supported by our findings here not just for the United States, but our other three cases as well.
Our results identify an additional concept important to understanding foreign policy attitudes -a factor we call 'global justice' -that captures support for more international redistribution. These notions of global justice represent a rich literature within international political theory that has, to date, been relatively under-explored within political behaviour and the literature on foreign policy attitudes (though see Bayram 2017;Noël & Thérien 2002;Spencer & Lindstrom 2013). This raises an important question: Why do we observe separate constructs for CI and global justice when early analyses (i.e., by Wittkopf) did not? 7 The answer here is interesting: our results finding that redistributive preferences constitute a distinct construct separate from cooperative internationalism actually is consistent with prior work.
In hindsight, we can see that some of the early work privileged the parsimony of a twofactor model while discarding concepts outside the MI/CI framework. Analysing the 1974 CCFR data, Maggiotto and Wittkopf (1981: 608) note clearly 'that the aid scales did not load with the traditional foreign policy scales [which] suggests that attitudes towards foreign aid are not intimately associated with other types of internationalist attitudes' . Wittkopf's (1990: 23) subsequent analyses of data from the 1978 and 1982 CCFR studies also show that responses to foreign aid questions cluster on their own to 'comprise quite distinctive orientations towards international involvement' .
In the Online Appendix, we employ modern estimation techniques to successfully replicate Mandelbaum and Schneider's (1978: 41-42) factor analysis of just 1974 CCFR questions pertaining to favouring or opposing a set of broad foreign policy goals that yields two dimensions they label 'Co-operative and Competitive Internationalism' . We extend this analysis to show a factor analysis of the goals questions with the addition of a single foreign aid question. Doing so yields results where a three-factor solution is superior to a two-factor solution. Importantly, responses to the foreign aid question load on a dimension with responses to the questions pertaining to the goals of 'combatting world hunger' and 'helping improving the standard of living elsewhere' . Thus, orientations toward global justice are not new; they simply form a previously under-appreciated dimension of public attitudes toward foreign policy. Further, differentiating clearly between cooperative and redistributive internationalism is important in understanding how domestic opinion imposes constraints on the foreign policies governments pursue. While public sentiment often opposes foreign assistance (while also substantially overestimating how much money is spent on aid), this does not imply public opposition to international cooperation.
Taken as a whole, the results in this article make key contributions. The first main finding is that mass publics are more nuanced in how they think about foreign policy than is usually acknowledged. Moving forward, research on foreign policy attitudes should therefore endeavour to measure orientations toward isolationism and global justice in addition to the familiar concepts of militant and cooperative internationalism. Failure to do so will yield an incomplete map of how mass publics view international politics. The second main finding is that the four factors identified are equivalent across the countries studied. There is, therefore, a firm statistical basis for cross-national comparisons of foreign policy attitudes. We might conclude by saying that we have four factors, and they travel across the North Atlantic.
These findings should nevertheless be viewed within the context of the data analysed. It is commonplace to note that factor analytic results are, to a degree, contingent upon what data one submits to such procedures. As we discuss above, we started with an unusually large target of possible constructs. Nevertheless, there are still gaps in what we capture. The foreign policy survey items we analyse do not contain any items dealing directly with trade, or many other aspects of international economic relations (though see Kleinberg & Fordham 2010). Consequently, there may be other foreign policy-related concepts in mass publics' collective minds that we have not uncovered here. Future research should endeavour to uncover such factors.
The results should also be understood as depicting the structure of foreign policy attitudes among the publics of four states, three of whom are nuclear-armed states, three of whom are -as of this writing -EU member states, and all of whom are NATO member states. In this sense, our study remains focused on advanced industrialised democracies with broad similarities to the well-studied American case. Our finding of scalar equivalence (or invariance) in foreign policy attitudes may be a function of the countries studied. Countries with vastly different histories, domestic institutions, capabilities or strategic contexts may be different in important ways. We are hopeful that the techniques we present for testing equivalence (combined with making our data available) will assist others in directly comparing foreign policy beyond the four cases we examine.
Our project here can also be viewed from a methodological perspective as a demonstration of the utility of modern statistical techniques, such as ESEM, for evaluating both the dimensionality and cross-national equivalence (or invariance) of social science concepts. The landscape of mass public opinion is often complex, as is the content of surveybased measures. By relaxing the sometimes untenable assumption of 'simple structure' while also providing a flexible and powerful statistical framework, ESEM offers social scientists a set of tools to model such complexity.
Finally, it is worth noting that our project here has been a largely inductive exercise in measurement. Future work should obviously endeavour to expand the number of countries analysed, and also provide a more theoretically developed account of why we observe country-level differences on the foreign policy dimensions. At the individual level, further research should also complete the Hurwitz and Peffley (1987) vertical constraint model in a systematic comparative fashion, with attention paid both to more abstract values above that shape these foreign policy postures (Goren et al. 2016;Kertzer et al. 2014;Rathbun et al. 2016), and to how these postures affect more specific policy attitudes across multiple countries and contexts. All of these lines of inquiry will deepen our knowledge of how mass publics organise their attitudes toward foreign policy. Our aim here has been to lay the groundwork for exactly these types of inquiries. Data Archive (Study Number 851142): http://dx.doi.org/10.5255/UKDA-SN-851142/. The use of nonprobability samples obtained by such matching methods is a topic of considerable discussion in the survey methodology literature. Some research focusing on the American context finds differences in estimates from probability and non-probability samples (e.g., Malhotra & Krosnick 2006), while other research finds few differences in the estimates obtained from matched sampling methods (such as those used by YouGov) and probability-based samples (Ansolabehere & Schaffner 2014). Research comparing survey modes focusing on the British context has found that differences are relatively small, and that substantive conclusions do not differ (Sanders et al. 2007). Additionally, an important criterion in the choice of sampling method is fit for purpose (Baker et al. 2013). Given that our focus is on discovering the underlying factor structure (as a type of correlational structure) in our survey data and not on specifying sample point estimates for individual survey items, we hold that there is a fit between our research aims and the use of matched samples. 5. Analyses were conducted using the Mplus program version 7.11 (Muthén & Muthén 2012). Models are estimated using robust weighted least squares with indicators treated as categorical data (Finney & DiStefano 2013). 6. It is also worth noting that responses to the question of whether 'in dealing with other nations' governments should be 'strong and tough' or 'understanding and flexible' perform poorly when included in our models. A similar item is a mainstay on leading American surveys such as the National Election Study (Hurwitz & Peffley 1987), but our wording of the question is shown in these analyses to have low cross-cultural validity. The 'go it alone in international affairs' indicator also performs poorly despite having resonance in American foreign policy (Nye 2002;Skidmore 2005) and French thought dating back to Louis XIV (Lynn 1999). 7. We thank Jason Roy and one of the EJPR anonymous reviewers for pressing us on this point.