Partisan Hostility and American Democracy, by James N. Druckman, Samara Klar, Yanna Krupnikov, Matthew Levendusky, and John Barry Ryan, is essential reading for those who fear that partisan hostility has pernicious consequences for mass-elite linkages as well as for the functioning (and ongoing degradation) of American democracy. The book delineates the conditions under which American citizens will fulfill James Madison’s hope that they be sufficiently knowledgeable and open-minded to hold their elected officials accountable. The authors present a rigorous theoretical and empirical analysis of how (and when) partisanship—and more particularly animus towards political opponents—affects contemporary American partisans’ beliefs and behaviors. This is an extremely insightful, provocative, and important book.

The authors theorize about and analyze the consequences of citizens’ cross-party hostility, whereby Democratic and Republican partisans increasingly view their political opponents with a mixture of fear, contempt, and dislike—a trend that has been in motion for at least 40 years. Partisan hostility is a component of the phenomenon of affective polarization, which has preoccupied American politics scholars (and, increasingly, comparativists) over the past decade. (The other component is in-party liking.) The authors offer a novel theory of when partisan animosity influences partisans’ policy preferences, their evaluations of political leaders (and other public figures and government agencies), their support for cross-party compromise, and their endorsement of democratic norms. The theory emphasizes animus towards political opponents—more so than warmth towards one’s in-party—as a force driving partisans’ beliefs and behaviors. However, the authors theorize that these effects are contingent: out-party animosity primarily moves partisans when the parties send strong, clear cues on the focal issue, and when, moreover, the issue does not have direct personal consequences. When either condition is absent, the effects of partisan animosity are muted.

The authors evaluate their arguments by analyzing a four-wave panel survey running from July 2019 to April 2021—a period that spanned the onset of the Covid-19 pandemic, followed by increasingly politicized controversies over pandemic-related public health policies, mass demonstrations for racial and social justice in response to the murder of George Floyd, Joe Biden’s defeat of Donald Trump in the 2020 presidential election, the January 6 insurrection at the US Capital, and President Trump’s subsequent impeachment. Crucially for the authors’ purposes, these events occurred after the first panel survey wave, so that the partisan animosity measures collected in July 2019—which comprised respondents’ out-party thermometer ratings, social distance measures, and out-partisan trust and trait ratings—can be viewed as causally prior to the attitudes and behaviors pertaining to these issues that survey respondents reported in subsequent panel waves. The authors also analyze citizens’ opinions over a wide range of other pre-existing issues. On some of these issues, the parties provided clear opposing cues (such as the Affordable Care Act and immigration), whereas on others, only one party provided a clear cue (including the Democrats’ support for an assault rifle ban and the Republicans’ opposition to the Green New Deal). Finally, the authors also examined other, nonpoliticized issues (e.g., negotiating lower drug prices for Medicare). The book then extends its analyses beyond issue debates to analyze linkages between animosity and partisans’ evaluations of public officials, their attitudes towards bipartisanship, and their support for democratic norms, including eschewing political violence.

The authors’ findings largely support their expectation of a conditional relationship between partisan animus and citizens’ beliefs and behaviors: animosity towards the out-party prompts high-animus partisans in particular to adjust their policy views along with their evaluations of public officials and agencies. The cases of Dr. Anthony Fauci and the Food and Drug Administration, for example, illustrate how party cues can politicize partisans’ evaluations of even nominally nonpartisan actors. However, these effects are mostly confined to domains where one or both parties stake out clear positions, and where the partisan does not confront a compelling personal stake. For instance, the authors conclude that the politicization of COVID-related debates over mask mandates and vaccinations had limited effects on partisans’ behavior in situations where they confronted the personal stakes of the illness. At the same time, high-animus partisans were especially resistant to political compromise by their own side (while advocating compromise from their opponents). The authors identify only weak effects with respect to popular support for many democratic norms, with even the most high-animus partisans largely rejecting political violence.

The book’s great strength is to pinpoint the conditional effects of partisan animus, an exercise that leads us to consider the wide range of issues on which citizens do not take party cues, either because the issue is not politicized and/or because the individual has a strong personal stake. Moreover, those partisans who do not significantly dislike their opponents (as the authors show, there are still some of them) are by definition immune to these partisan animus effects. This perspective offers an antidote to the view of partisanship as an all-encompassing identity that shapes nearly every dimension of partisans’ political beliefs and behaviors. This is a valuable contribution. Moreover, the authors scrupulously highlight the limitations of their observational analyses for making causal inferences, while also emphasizing additional challenges in distinguishing between the effects of out-party animus—the phenomenon they highlight—versus the effects of in-party liking and other related worldviews. This is one of the best books on political behavior I have ever read.

One of the most valuable parts of the book is the final chapter, which addresses the implications of the authors’ findings for the possibility of various forms of system malfunction, including political paralysis, widespread political violence, and democratic backsliding. Here. the authors highlight the possible limits of their findings that partisans mostly support democratic norms, noting that, over time, skillful political leaders may weaponize partisans’ fear and dislike of opponents to roll back democracy one step at a time—a process that citizens of Hungary and Poland have recently experienced. Like the frog that fails to notice that the water has slowly come to a boil, hateful partisans may fail to recognize that canny elites are gradually rolling back democracy. Thus, the authors emphasize that the future of American democracy depends largely on the behaviors and values of politicians. Here, recent events do not summon optimism. Since the authors’ 2019–2021 panel survey concluded, we have witnessed Democratic party elites’ near total refusal to acknowledge President Biden’s physical and cognitive deterioration (at least prior to the July 2024 presidential debate), along with Republican representatives’ ongoing acquiescence as the second Trump administration tears the fabric of democratic norms, practices, and institutions. Yet both parties’ elites assiduously denounce their opponents for dereliction of their democratic duty. The point here is not that both parties’ sins are equivalent, but that politicians—like ordinary citizens—are much more effective at recognizing and confronting problematic elite behavior when it is practiced by the other side. The authors of Partisan Hostility and American Democracy masterfully analyze how partisan animus shapes rank-and-file Americans’ opinions and behaviors. The question remains how many American elites—in many cases the ultimate angry partisans—are prepared to actively oppose (or even recognize) actions from their own side of the aisle that degrade democracy. Our political system’s future likely depends on the answer.