The Rise of Partisan Rigidity: The Nature and Origins of Partisan Extremism in American Politics

Abstract

As political elites have polarized, the American public has become more strongly partisan. Why has the American public become more extremely partisan, and what does this transformation of the electorate imply for the health of American democracy? In this thesis, I argue that elite polarization has strengthened the relationship between a basic psychological motivation for group membership—the need for certainty—and partisan strength, in-party favoritism, out-party derogation, and conformity to group leaders. Because the need for certainty is a form of motivated closed-mindedness, I argue that the American electorate today is increasingly composed of rigid partisans: partisans who are uncritically extremist, biased, and intolerant. Across a number of distinct empirical studies, this thesis demonstrates that, (1) partisan strength, in-group favoritism, out-group derogation and partisan sorting have a strong basis in the psychological need for certainty, (2) in many cases this pre-political psychological variable has larger effects on partisan strength than explicitly political variables such as policy preferences, (3) that this effect occurs among both Democrats and Republicans, (4) that this has caused politically engaged respondents in particular to be rigid in their partisan identity, and (5) that this relationship has grown stronger over time as political elites have polarized and become more internally cohesive and distinct. In conclusion, I argue that the transformation of the public into rigid partisans weakens the competence of the American electorate and threatens the foundations of American democracy.