Political Parties as Drivers of U.S. Polarization: 1927-2018

74 Pages Posted: 4 Jan 2021 Last revised: 25 Apr 2022

See all articles by Nathan Canen

Nathan Canen

University of Houston

Chad Kendall

University of Southern California

Francesco Trebbi

University of California, Berkeley - Haas School of Business; National Bureau of Economic Research (NBER)

Date Written: December 2020

Abstract

The current polarization of elites in the U.S., particularly in Congress, is frequently ascribed to the emergence of cohorts of ideologically extreme legislators replacing moderate ones. Politicians, however, do not operate as isolated agents, driven solely by their preferences. They act within organized parties, whose leaders exert control over the rank-and-file, directing support for and against policies. This paper shows that the omission of party discipline as a driver of political polarization is consequential for our understanding of this phenomenon. We present a multi-dimensional voting model and identification strategy designed to decouple the ideological preferences of lawmakers from the control exerted by their party leadership. Applying this structural framework to the U.S. Congress between 1927- 2018, we find that the influence of leaders over their rank-and-file has been a growing driver of polarization in voting, particularly since the 1970s. In 2018, party discipline accounts for around 65% of the polarization in roll call voting. Our findings qualify the interpretation of - and in two important cases subvert - a number of empirical claims in the literature that measures polarization with models that lack a formal role for parties.

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Suggested Citation

Canen, Nathan and Kendall, Chad and Trebbi, Francesco, Political Parties as Drivers of U.S. Polarization: 1927-2018 (December 2020). NBER Working Paper No. w28296, Available at SSRN: https://ssrn.com/abstract=3759833

Nathan Canen (Contact Author)

University of Houston ( email )

4800 Calhoun Road
Houston, TX 77204
United States

Chad Kendall

University of Southern California ( email )

USC FBE Dept.
701 Exposition Blvd, Ste. 231 HOH-231, MC-1422
Los Angeles, CA 90089
United States

HOME PAGE: http://https://www.sites.google.com/site/chadwkendall/

Francesco Trebbi

University of California, Berkeley - Haas School of Business ( email )

545 Student Services Building, #1900
2220 Piedmont Avenue
Berkeley, CA 94720
United States

National Bureau of Economic Research (NBER) ( email )

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Cambridge, MA 02138
United States

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