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A Double-Edged Sword? How Appeals to Group Identity May Shape Affective Polarization & Political Mobilization


Democrats and Republicans in the United States have become increasingly hostile toward and distrustful of one another over the past five decades. This dissertation documents the rise of this phenomenon, which is called affective polarization, and develops and tests a novel theory to explain it.

Affective polarization has its roots the changing demographic composition of the two parties. The Democratic Party is increasingly non-white, educated, urban, non-religious, while the Republican Party remains overwhelmingly white, religious, and conservative. Previous work has tied these shifts to the increase in inter-party hostility but has been unable to show how exactly the process works.

This dissertation attempts to fill this gap in understanding with the argument that elite communication is the essential intermediate step in the transformation of demographic social sorting and into affective polarization. Specifically, political elites’ appeals make group identities salient considerations, activating stereotypes about who belongs in each party. Political actors make these appeals in speeches, campaign ads, and news reports because they more are effective tools for mobilizing and persuading voters than appeals based on policy or ideology. And as core social identities such as race, class, religiosity, urbanicity, and age increasingly align with partisanship, the incentive to political actors to play to them become stronger.

In making these appeals to Americans’ social identities, partisans’ understanding of what a typical Democrat and typical Republican look like solidifies, making it easier to demonize members of the opposite party. These increased stereotypes lead to affective polarization among the American public. In other words, social identity alignment does not engender affective polarization in and of itself; the later results only as political communication activates aspects of individuals’ personas in the service of political goals. Increased inter-party hostility is an unfortunate by-product of this mobilizing rhetoric.

To test this theory, I examine the way that political elites have communicated shifts in the party composition since the 1970s. I use a multi-pronged methodological approach, combining longitudinal survey data, text analysis, and survey experiments to test each link in my chain of argument: 1) that the parties have grown increasingly distinct over time, 2) that political elites communicate these changes in their rhetoric, and 3) that exposure to appeals to group identity can increase affective polarization.

Overall, the results of this research are mixed. I find robust evidence that affective polarization has occurred among broad swaths of the American electorate, and confirm the findings of Mason (2018) that social group sorting has occurred during that same time period. Further, I demonstrate that the language that party elites used to describe their priorities and goals tracks these changing party coalitions, with appeals to group identities increasing most sharply within the Democratic Party. However my research on the effects of exposure to group appeals produced mixed results, supporting expectations in some experimental tests and disappointing them in others. My overall conclusion from this research is that the theoretical premise of this dissertation, which posits a central role for elite communication in causing affective polarization, remains promising but will require more refined tests to confirm or refute.

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