Geography, Uncertainty, and Polarization *

Abstract

Abstract Using new data on roll-call votes of U.S. state legislators and measures of public opinion in their districts, we explain how ideological polarization of voters within districts can lead to legislative polarization. Many of the so-called "moderate" districts that switch hands between Democrats and Republicans are internally polarized. The ideological distance between Democrats and Republicans within these districts is often greater than the distance between liberal cities and conservative rural areas. We present a theoretical model in which intra-district ideological polarization causes candidates to be uncertain about the ideological location of the median voter, thereby reducing their incentives to moderate their policy positions. We then demonstrate that in districts with similar median voter ideologies, the difference in roll-call voting behavior between Democratic and Republican state legislators is greater when there is more within-district ideological heterogeneity. Our findings suggest that accounting for the subtleties of political geography can help explain the coexistence of a polarized legislature and a moderate mass public