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Does Gerrymandering Cause Polarization?


  • We would like to thank seminar participants at Berkeley, Caltech, Harvard, Ohio State, Princeton, Rochester, Stanford, Conference on Designing Democratic Institutions at LSE, and the Russell Sage Inequality meetings.

Nolan McCarty is Susan Dod Brown Professor of Politics and Public Affairs, Woodrow Wilson School, Princeton University, Princeton, NJ 08540 ( Keith T. Poole is Professor of Political Science, University of California, San Diego, La Jolla, CA 92093-0521 ( Howard Rosenthal is Professor of Politics, New York University, 19 W. 4th Street, New York, NY 10012 (


Both pundits and scholars have blamed increasing levels of partisan conflict and polarization in Congress on the effects of partisan gerrymandering. We assess whether there is a strong causal relationship between congressional districting and polarization. We find very little evidence for such a link. First, we show that congressional polarization is primarily a function of the differences in how Democrats and Republicans represent the same districts rather than a function of which districts each party represents or the distribution of constituency preferences. Second, we conduct simulations to gauge the level of polarization under various “neutral” districting procedures. We find that the actual levels of polarization are not much higher than those produced by the simulations. We do find that gerrymandering has increased the Republican seat share in the House; however, this increase is not an important source of polarization.