Jeffrey M. Stonecash is Maxwell Professor in the Maxwell School, Syracuse University. He researches political parties, changes in their electoral bases, and how these changes affect political polarization and public policy debates. His recent books are Class and Party in American Politics (2000), Diverging Parties (2002), Political Polling (2003), Parties Matter (2005), and Split: Class and Cultural Divisions in American Politics (2007). He is now working with Mark Brewer on a book about the dynamics of party realignment since 1900. He has done polling and consulting for political candidates since 1985.

• Part I. An Increased Incumbency Effect: Reconsidering Evidence: 1. An increased incumbency effect and American politics; 2. The consensus about a greater incumbency effect; 3. The trend in incumbent vote percentages; 4. Cumulative career changes; 5. The retirement slump; Part II. Realignment and the Fortunes of (Some) Incumbents: 6. An alternative framework: the role of realignment; 7. A partisan view of incumbent percentages; 8. The role of realignment; 9. Conclusions and implications; Part III. Appendices: More Detailed Analyses of Incumbency Indicators: Appendix A. The Gelman–King estimation; Appendix B. Realignment and the retirement slump; Appendix C. The data.