Dealing in Discipline: Party Switching and Legislative Voting in the Italian Chamber of Deputies, 1988–2000


  • The authors thank the Chamber of Deputies' Office of Parliamentary Services for data, Robin Best for research assistance, and Timothy Nokken, Olga Shvetsova, and other members of the Party Switching Research Group, Brian Humes, Wendy Martinek, Michael McDonald, Anthony Mughan, Mauro Paissan, Howard Rosenthal, Kaare Strøm, and the anonymous referees for helpful comments and suggestions. Both authors recognize support from the National Science Foundation (NSF SES-0339920 for Heller and NSF SES-0339877 for Mershon).

William B. Heller is associate professor of political science, Binghamton University, P.O. Box 6000, Binghamton, NY 13902–6000 ( Carol Mershon is associate professor of politics, University of Virginia, P.O. Box 400787, Charlottesville, VA 22904-4787 (


Compared to U.S. political parties, parties in Italy (and Europe generally) are quite cohesive. Rarely do members of parliament vote against their copartisans in legislative divisions. Yet in Italy in recent years, legislators switch parties with seeming abandon. Between 1996 and spring 2000, one out of four deputies in the Chamber of Deputies switched parties at least once, compared to only 20 switches in the U.S. Congress from 1947 to 1997 (Nokken 2000). We examine the relationship between switching and observed party unity in Italy by focusing on individual legislators' switching decisions and voting behavior. Overall, switchers move out of highly disciplined parties, suggesting that they switch partly in order to escape strong discipline.