Date of Award

Fall 12-2018

Degree Type


Degree Name


Degree Program

Political Science


Political Science

Major Professor

Christine L. Day

Second Advisor

Daniel C. Lewis

Third Advisor

Marc R. Rosenblum


Since the mid-1970s, partisan polarization has been increasing in Congress and the Presidency, and, although most voters lack a stable, consistent ideology, non-ideological forms of partisan polarization have emerged in the mass public in recent decades. Moreover, ideological polarization among elites is highly asymmetrical, with increased Republican conservatism accounting for most of the increased ideological distance between the parties. Here, I develop a racial-threat backlash theory and argue that increased rates of immigration are associated with increased asymmetrical ideological polarization among elites and in the mass public. Tests of this theory on voters, the mass public in the states, state legislators, and Senators provide support for my theory. In addition, when accounting for the effects of immigration, I do not find support for the alternative explanation that increased income inequality leads to increased asymmetrical partisan polarization.


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