American Political Science Review

Determinants of the Outcomes of Midterm Congressional Elections  *

Edward R. Tufte

Princeton University


An explanatory model for the outcomes of midterm congressional elections is developed. Midterms are a referendum on the performance of the President and his administration's management of the economy. The explanatory model of midterm congressional elections is sufficiently powerful so as to yield honest and accurate pre-election predictions of the national two-party vote in midterm elections. These predictions have usually outperformed pre-election forecasts based on survey data. The model is extended by considering the translation of votes into seats, models of the electorate as a whole and of the individual voter, and the causes of the off-year loss by the President's party.

Edward R. Tufte, Professor of Public Affairs, Princeton University.


*  I wish to thank Marge Cruise, Jan Juran, Alice Anne Navin, Susan Spock, Michael Stoto, and Richard Sun for their help in the collection and analysis of the data. John L. McCarthy, Richard A. Brody, Gerald H. Kramer, Duane Lockard, David Seidman, and Jack Walker provided advice and encouragement. Financial support came from the Woodrow Wilson School of Public and International Affairs at Princeton University and from a fellowship at the Center for Advanced Study in the Behavioral Sciences. Early drafts of the paper were presented in seminars at the Center (October, 1973); the Bay Area Political Behavior Seminar (January, 1974); and Princeton University (October, 1974). A partial, preliminary version of the model is reported in Edward R. Tufte, Data Analysis for Politics and Policy (Englewood Cliffs, New Jersey: Prentice-Hall, 1974), pp. 140–145. I wish also to thank several anonymous reviewers and Dr. Ellen Y. Siegelman of the Review for their helpful comments. These individuals and institutions do not, of course, bear responsibility for the faults of the study.