Assessing the External Validity of Election RD Estimates: An Investigation of the Incumbency Advantage

33 Pages Posted: 11 Feb 2014 Last revised: 6 Dec 2015

See all articles by Jens Hainmueller

Jens Hainmueller

Stanford University - Department of Political Science; Stanford Graduate School of Business; Stanford Immigration Policy Lab

Andrew Hall

Stanford University

James M. Snyder

Harvard University

Date Written: February 27, 2014

Abstract

The electoral regression discontinuity (RD) design is popular because it provides an unbiased, design-based estimate of the incumbency advantage with few assumptions. However, as is well known, the RD estimate is "local": it only identifies the effect in hypothetical districts with an exactly 50-50 tie between the Democratic and Republican candidates, and does not speak to the size of the incumbency advantage away from this threshold. There is significant uncertainty over the effect of incumbency in districts away from this threshold. Indeed, in a survey of political scientists that we administered, roughly equal numbers of respondents predict the effect to be either larger, smaller, or the same in less competitive districts. In this paper, we follow the method proposed in Angrist and Rokkanen (2013), employing a validated Conditional Independence Assumption that, unlike in typical cases, generates directly testable implications in the context of the RD. This technique allows us to estimate the average effect of incumbency in districts in a window around the threshold as large as 15 percentage points -- i.e., elections in which the winning candidate secured as much as 57.5% of the two-party vote. We find that the incumbency advantage is no larger or smaller in these less competitive districts.

Suggested Citation

Hainmueller, Jens and Hall, Andrew and Snyder, James M., Assessing the External Validity of Election RD Estimates: An Investigation of the Incumbency Advantage (February 27, 2014). Journal of Politics. 77(3): 707-720. 2015.; Stanford University Graduate School of Business Research Paper No. 14-02. Available at SSRN: https://ssrn.com/abstract=2393611 or http://dx.doi.org/10.2139/ssrn.2393611

Jens Hainmueller (Contact Author)

Stanford University - Department of Political Science ( email )

Stanford, CA 94305
United States

HOME PAGE: http://www.stanford.edu/~jhain/

Stanford Graduate School of Business ( email )

655 Knight Way
Stanford, CA 94305-5015
United States

Stanford Immigration Policy Lab

30 Alta Road
Stanford, CA 94305
United States

Andrew Hall

Stanford University ( email )

Stanford, CA 94305
United States

James M. Snyder

Harvard University ( email )

1875 Cambridge Street
Cambridge, MA 02138
United States

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