American Political Science Review

Research Article

The Case for Responsible Parties


a1 University of Illinois at Urbana-Champaign

a2 University of Rochester

a3 Universita' degli Studi di Brescia and Essex University


Electoral platform convergence is perceived unfavorably by both the popular press and many academic scholars. Arguably, to paraphrase, “it does not provide enough choice” between candidates. This article provides a formal account of the perceived negative effects of platform convergence. We show that when parties do not know voters' preferences precisely, all voters ex ante prefer some platform divergence to convergence at the ex ante median. After characterizing the unique symmetric equilibrium of competition between responsible (policy-motivated) parties, we conclude that all voters ex ante prefer responsible parties to opportunistic (purely office-motivated) ones when parties are sufficiently ideologically polarized that platforms diverge, but not so polarized that they diverge excessively. However, greater polarization increases the scope for office benefits as an instrument for institutional design. We calculate the socially optimal level of platform divergence and show that office benefits can be used to achieve this first-best outcome, if parties are sufficiently ideologically polarized.


c1 Dan Bernhardt is IBE Distinguished Professor of Economics and Finance, University of Illinois at Urbana-Champaign, 1106 S. Prospect Avenue, Champaign, IL 61820 (

c2 John Duggan is Professor of Political Science and of Economics, W. Allen Wallis Institute of Political Economy, University of Rochester, Rochester, NY 14627 (

c3 Francesco Squintani is Professore Ordinario di Economia Politica, Universita' degli Studi di Brescia; and, Professor of Economics, University of Essex, Wivenhoe Park, Colchester, Essex CO4 3SQ, United Kingdom (


We thank Becky Morton, Michael Peress, and Joao Santos for valuable conversations. All mistakes are our own.