American Political Science Review

Research Article

Activists and Conflict Extension in American Party Politics


a1 University of Notre Dame

a2 University of North Carolina at Chapel Hill

a3 University of Akron

a4 Arizona State University

a5 University of Mary Washington


Party activists have played a leading role in “conflict extension”—the polarization of the parties along multiple issue dimensions—in contemporary American politics. We argue that open nomination systems and the ambitious politicians competing within those systems encourage activists with extreme views on a variety of issue dimensions to become involved in party politics, thus motivating candidates to take noncentrist positions on a range of issues. Once that happens, continuing activists with strong partisan commitments bring their views into line with the new candidate agendas, thus extending the domain of interparty conflict. Using cross-sectional and panel surveys of national convention delegates, we find clear evidence for conflict extension among party activists, evidence tentatively suggesting a leading role for activists in partisan conflict extension more generally, and strong support for our argument about change among continuing activists. Issue conversion among activists has contributed substantially to conflict extension and party commitment has played a key role in motivating that conversion.


c1 Geoffrey C. Layman is Associate Professor, Department of Political Science, University of Notre Dame, 217 O'Shaughnessy Hall, Notre Dame, IN 46556 (

c2 Thomas M. Carsey is Pearsall Distinguished Professor of Political Science, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599 (

c3 John C. Green is Distinguished Professor of Political Science, University of Akron, 223B Olin Hall, Akron, OH 44325 (

c4 Richard Herrera is Associate Professor, School of Politics and Global Studies, Arizona State University, Coor Hall, 6th Floor, Tempe, AZ 85287 (

c5 Rosalyn Cooperman is Assistant Professor, Department of Political Science and International Affairs, University of Mary Washington, 1301 College Avenue, Fredericksburg, VA 22401 (


Previous versions of this article were presented at the University of Maryland, University of North Carolina, University of Notre Dame, Stanford University, Indiana University, and the annual meeting of the Southern Political Science Association. The authors thank everyone who attended those presentations for helpful feedback. We thank John Aldrich, Jim Guth, Frances Lee, Michael MacKuen, and the anonymous reviewers and co-editors of the American Political Science Review. We are very grateful to Anne Cizmar and Ozan Kalkan for generous research assistance. Finally, we thank the Ray C. Bliss Institute for Applied Politics at the University of Akron, Arizona State University, Florida State University, University of Maryland, and University of Mary Washington for providing the funds necessary to conduct some of the surveys used in the article. Any errors or problems that remain are the responsibility of the authors alone.