Are Close Elections Random?∗

Elections with small margins of victory represent an important form of democratic competition and, increasingly, an opportunity for causal inference. When scholars use close elections for examining competition or for causal inference, they impose assumptions about the politics of close contests: campaigns are unable to systematically determine the outcome. This paper calls into question this model and introduces a new model that accounts for strategic campaign behavior. We draw upon the intuition that elections that are expected to be close attract greater campaign efforts before the election and invite legal challenges and fraud after the election. Our theoretical models predict systematic differences between winners and losers in extremely close elections. We test our predictions using all House elections from 1880-2008, finding that structurally advantaged candidates are more likely to win close elections. But the structural advantages that predict winners shift over time: from 1880 to the 1960’s, candidates from strong parties are systematically more likely to win close contests, but the advantage dissipates in more recent contests. After the 1940’s, incumbent candidates are much more likely to win close elections. Our findings suggest a new research agenda on the systematic determination of close contests. ∗We thank Dan Lee for helpful discussant comments and participants at the Midwest Political Science Association Annual Conference and seminar participants at Stanford and Harvard University. For helpful discussions and data we thank Lisa Blaydes, Daniel Butler, Devin Caughey, Gary Cox, Andy Eggers, James Fearon, Jens Hainmueller, Daniel Hopkins, Guido Imbens, David Laitin, David Lee, Simon Jackman, Jeff Jenkins, Holger Kern, Gary King, Clayton Nall, Jonathan Rodden, Jas Sekhon, Erik Snowberg, Jim Snyder, Jonathan Wand and Arjun Wilkins. All remaining errors, omissions, and interpretations remain ours. †Assistant Professor, Department of Political Science, Stanford University; Encina Hall West 616 Serra St., Palo Alto, CA, 94305. Corresponding Author. ‡Assistant Professor, Department of Political Science, Yale University; 77 Prospect St., New Haven, CT 06520. §J.D. candidate, Harvard Law School. ¶Allie S. Freed Professor of Government. Department of Government, Harvard University. 1737 Cambridge St., Cambridge, MA 02138.