2025 Theses Doctoral

"The Enemy Is Within": Essays on Elite Affective Polarization in American Politics

Frederick, Samuel

Antipathy toward members of the opposing political party has risen in recent years in the United States.Partisan hostility in American legislatures has escalated to the point that some legislators fear violence from their peers across the aisle. Amid this increase in partisan tension, bipartisanship in lawmaking has declined. Existing theoretical frameworks of legislative behavior struggle to explain the extent of inter-partisan animosity, however. This dissertation examines whether affective polarization, hatred of the opposing party and warmth toward one's own, can explain increasing partisan conflict among politicians. In particular, using experiments embedded in original surveys of American politicians, I explore the consequences of partisan animus among politicians for democratic governance. I also probe the causes of partisan hostility among political elites.

In the first empirical chapter of my dissertation, I argue that, due to the hyper-salience of legislators' political identities, partisan identities may be important in shaping the behavior of American politicians. Results from a conjoint experiment in an original survey of state legislative candidates show that politicians discriminate against members of the opposing party when selecting partners in the policy-making process. Affectively polarized politicians are especially likely to choose to work with a co-partisan legislator over an out-partisan. While policy information appears to account for much of this partisan discrimination, more affectively polarized candidates are more likely than their less polarized peers to choose a co-partisan partner---even when a great deal of policy information is provided. These results have important implications for the study of legislative politics, affective polarization, and American democracy.

Next, I turn to the causes of affective polarization among politicians. While previous research evaluates the individual-level or intergroup drivers of affective polarization, less work has considered the intragroup social determinants of partisan animosity. The second empirical chapter of this dissertation demonstrates how intra-party social norms constrain and shape affective polarization at the mass and politician levels. I focus on norms against the expression of partisan incivility. Using original surveys of elected officials and the American public, I show that there is a strong norm against partisan incivility among politicians, but the norm among the mass public favors partisan incivility. Within my surveys, I embed experiments to evaluate the causal effects of priming this social norm on affective polarization. I find tentative support for the idea that social norms around partisan incivility can influence hostility toward the opposing party. In addition, inparty norms increase warmth toward the inparty, suggesting a potential normative basis for inparty identity. My findings shed light on the social roots of affective polarization, offering a deeper understanding of the causes of partisan animosity in American politics.

Finally, in my third empirical chapter, I show that politicians are most hostile toward out-party activists, followed by politicians and finally, by voters. My survey highlights an asymmetry in politicians' perceptions of the parties: politicians' feelings toward the out-party are closest, on average, to their feelings toward out-party activists, while politicians seem to distinguish their own party from its activists. This gap in attitudes toward the parties appears to increase affective polarization among politicians.