Public Opinion and the Democratic Peace MICHAEL R
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American Political Science Review Vol. 107, No. 4 November 2013 doi:10.1017/S0003055413000488 c American Political Science Association 2013 Public Opinion and the Democratic Peace MICHAEL R. TOMZ Stanford University JESSICA L. P. WEEKS University of Wisconsin–Madison ne of the most striking findings in political science is the democratic peace: the absence of war between democracies. Some authors attempt to explain this phenomenon by highlighting the role O of public opinion. They observe that democratic leaders are beholden to voters and argue that voters oppose war because of its human and financial costs. This logic predicts that democracies should behave peacefully in general, but history shows that democracies avoid war primarily in their relations with other democracies. In this article we investigate not whether democratic publics are averse to war in general, but whether they are especially reluctant to fight other democracies. We embedded experiments in public opinion polls in the United States and the United Kingdom and found that individuals are substantially less supportive of military strikes against democracies than against otherwise identical autocracies. Moreover, our experiments suggest that shared democracy pacifies the public primarily by changing perceptions of threat and morality, not by raising expectations of costs or failure. These findings shed light on a debate of enduring importance to scholars and policy makers. ew findings in political science have received as gated whether democratic publics are more reluctant much attention as the “democratic peace,” the to attack democracies than autocracies.1 Moreover, the Fdiscovery that democracies almost never fight small body of existing work has not accounted for other democracies (Doyle 1986; Russett 1993). To variables that could confound the relationship between some, the absence of military conflict among democ- shared democracy and public support for war, nor has racies is so consistent that it approaches the status of it investigated the mechanisms by which the regime an “empirical law” (Levy 1988). type of the adversary affects the public mood. Despite Some authors have attempted to explain the demo- decades of research on the democratic peace, we still cratic peace by highlighting the role of public opinion. lack convincing evidence about whether and how pub- They observe that democratic leaders are beholden to lic opinion contributes to the absence of war among voters and claim that voters oppose war because of democracies. its human and financial costs. This argument, which We used experiments to shed new light on these dates to Immanuel Kant, predicts that democracies important questions.2 Our experiments, embedded in will behave peacefully in general—avoiding war not public opinion polls that were administered to nation- only against democracies but also against autocracies. ally representative samples of British and American History shows, however, that democracies frequently citizens, involved a situation in which a country was fight autocracies. developing nuclear weapons. When describing the sit- A different possibility is that democratic publics are uation, we randomly and independently varied four primarily averse to war against other democracies. If potential sources of peace: the political regime, alliance leaders are responsive to voters and voters are more status, economic ties, and military power of the adver- reluctant to fight democracies than otherwise equiv- sary. We then asked individuals whether they would alent autocracies, then public opinion could play an support or oppose a preventive military strike against important role in the dyadic democratic peace. To the country’s nuclear facilities. date, however, surprisingly few studies have investi- Participants in our experiments were substantially less supportive of military strikes against democracies than against otherwise identical autocracies. Moreover, Michael R. Tomz is Professor of Political Science, Stanford because we randomly and independently manipulated University ([email protected]). Jessica L. P. Weeks is Assistant Professor of Political Science, the regime type of the adversary, the observed pref- University of Wisconsin–Madison ([email protected]). erence for peace with other democracies was almost We are grateful for helpful feedback from Ted Brader, Alexandre certainly causal, rather than spurious. Our findings Debs, James Fearon, Erik Gartzke, Michael Horowitz, Kosuke Imai, therefore provide empirical microfoundations for the Robert Johns, Peter Katzenstein, Sarah Kreps, Bethany Lacina, Brad Laveck, Ashley Leeds, Cliff Morgan, Jim Morrow, Jon Pevehouse, Lauren Prather, Bill Reed, Bruce Russett, Scott Sagan, ToddSechser, 1 For exceptions, see Geva, DeRouen, and Mintz (1993); Johns and Branislav Slantchev, Paul Sniderman, Art Stein, Dustin Tingley, Davies (2012); Mintz and Geva (1993), and Rousseau (2005). See Rob Van Houweling, Teppei Yamamoto, three anonymous review- also Lacina and Lee (2012), who examine how regime type affects ers, and the American Political Science Review editorial board. We perceptions of threat, and Geva and Hanson (1999), who focus on thank seminar participants at Georgetown, Michigan, Rice, Stan- sociocultural similarity. ford, University of California, Los Angeles, University of California, 2 For other recent examples of experiments about international se- San Diego, University of Virginia, and Yale, and conference partic- curity, see Herrmann, Tetlock, and Visser (1999); Herrmann and ipants at Harvard, Princeton, Tel Aviv University, the International Shannon (2001); Berinsky (2007; 2009); Gartner (2008); Baum and Studies Association, the Midwest Political Science Association, and Groeling (2009); Gelpi, Feaver, and Reifler (2009); Grieco et al. the European Consortium for Political Research. We are grateful (2011); Horowitz and Levendusky (2011); McDermott (2011); Tin- to Ray Duch and Inaki˜ Sagarzazu for invaluable help with the gley (2011); Tingley and Walter (2011); Tomz (2007); Trager and British survey, and to the National Science Foundation for Grant Vavreck (2011); Levendusky and Horowitz (2012), and Press, Sagan, SES-0548285. and Valentino (2013). 849 Public Opinion and the Democratic Peace November 2013 hypothesis that the preferences of ordinary voters con- a role in electoral campaigns, and that foreign policy tribute to peace among democracies. mistakes can hurt leaders at the ballot box (Aldrich, In addition to estimating the overall effect of democ- Sullivan, and Borgida 1989; Gelpi, Reifler, and Feaver racy, we investigated the mechanisms through which 2007; Gronke, Koch, and Wilson 2003). shared democracy reduces public enthusiasm for war. Second, democratic leaders face institutional con- Democratic publics may feel reluctant to attack other straints on their powers to use force (Morgan and democracies for a variety of reasons: They may view Campbell 1991), and public opinion affects how tightly democracies as less threatening (Risse-Kappen 1995; those constraints bind. In many democracies, leaders Russett 1993), regard democracies as more formidable need legislative authorization for war, but legislative opponents (Bueno de Mesquita et al. 1999; Lake 1992; approval is less likely to materialize in the face of pub- Reiter and Stam 2002), or have moral qualms about lic opposition (Hildebrandt et al. 2013; Lindsay 1994). using force to overturn policies that were freely cho- Moreover, leaders must raise revenues to pay for mil- sen by citizens in another democracy. Despite vol- itary operations, but legislative bodies are unlikely to umes of research about the democratic peace, how- levy new taxes, incur new debt, or cut government pro- ever, little is known about whether these factors grams to finance wars that their constituents oppose influence the willingness of voters to attack other (Hartley and Russett 1992; Narizny 2003). democracies. Third, leaders understand that, by remaining pop- Using a unique experimental design and new tech- ular, they can accomplish more during their time niques for causal mediation analysis (Imai et al. 2011; in office. In the United States, for example, pop- Imai, Keele, and Yamamoto 2010), we find that shared ular presidents have more influence over Congress democracy pacifies the public primarily by changing (Edwards 1997; Howell and Pevehouse 2007; Krosnick perceptions of threat and morality, not by raising ex- and Kinder 1990). They also wield more international pectations of costs or failure. Individuals who faced influence, because leaders who enjoy the backing of democratic rather than autocratic countries were less the public find it easier to persuade other countries fearful of the country’s nuclear program and harbored that their promises and threats are credible. greater moral reservations about attacking. Those per- Consistent with these arguments, countless stud- ceptions, in turn, made citizens more peaceful to- ies have concluded that, in decisions about using ward democracies. By comparison, respondents did force, democratic leaders pay close attention to pub- not think that attacking a democracy would result in lic opinion (Baum 2004; Baum and Potter 2008; substantially higher costs or a lower likelihood of suc- Berinsky 2009; Canes-Wrone 2006; Foyle 1999; Holsti cess than attacking an autocracy. Thus, our data help 2004; Mueller 1973; Reiter and Stam 2002; Rosenau arbitrate between competing mechanisms, while also 1961; Russett 1990; Sobel 2001). Studying the pub- identifying morality