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Field Experiments Testing the Impact of Radio Advertisements on Electoral Competition


  • The authors are indebted to Alan Gerber, who helped shape this project, and to Shang Ha, Peter Wielhouwer, Robert Entman, Jeffrey Cohen, Richard Fleisher, Bruce Berg, and Bart Robbett, who provided many useful suggestions. We are also grateful to the Institution for Social and Policy Studies at Yale University, which funded this research but bears no responsibility for the conclusions we reach. This experiment was reviewed and approved by the Human Subjects Committee at Yale University.

Costas Panagopoulos is assistant professor of political science, Fordham University, 441 E. Fordham Rd., Bronx, NY 10458 ( He is also a research fellow at the Institution for Social and Policy Studies at Yale University. Donald P. Green is A. Whitney Griswold professor of political science and director of the Institution for Social and Policy Studies, Yale University, 77 Prospect Street, P.O. Box 208209, New Haven, CT (


Results from previous studies of campaign spending imply that equal-sized grants to both incumbents and challengers are a net benefit to challengers, who on average spend less money and derive greater marginal returns from each additional dollar. This study provides an experimental test of this proposition. Cities holding mayoral elections in November 2005 and 2006 were randomly assigned to broadcast nonpartisan radio ads that stated the names of the mayoral candidates, reminded listeners about the date of the upcoming election, and encouraged them to vote. Consistent with the findings of previous studies on the differential effects of incumbent and challenger campaign spending on election outcomes, we find that these radio ads produced substantially more competitive elections. The borderline statistical significance of our results, however, invites replication of this experiment.