Partisan Subconstituencies and Polarization in the U.S.

42 Pages Posted: 16 Sep 2019

See all articles by Daniel Butler

Daniel Butler

University of California San Diego

Date Written: September 6, 2019


I study the change in polarization in the U.S. Senate from the period 1947-1966 to 1995-2014. I use a decomposition approach to quantify how much of the increase in polarization over that period can be explained by the representation relationship with all voters versus the representation relationship with copartisans. The decomposition also identifies the portion that arose from voters changing positions and how much arose from politicians changing how responsive they are to voters. I find that the representation relationship explains a majority of the increase in polarization. Further, I find that Republicans have become more conservative because they have become more responsive to the positions of their copartisan base. Copartisan subconstituencies matter for representation and are a source of increased polarization.The data also shows Democrats have contributed to polarization because the overall electorate in their districts have become more socially liberal.

Keywords: Polarization, American politics, Primary elections

JEL Classification: H10

Suggested Citation

Butler, Daniel, Partisan Subconstituencies and Polarization in the U.S. (September 6, 2019). Available at SSRN: or

Daniel Butler (Contact Author)

University of California San Diego ( email )

Social Sciences Building
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La Jolla, CA 92093-0521
United States
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