American Political Science Review

Research Article

Leapfrog Representation and Extremism: A Study of American Voters and Their Members in Congress


a1 Dartmouth College


We consider the relationship between the preferences of American voters and the preferences of the U.S. legislators who represent them. Using an Internet-based, national opinion survey in conjunction with legislator voting records from the 109th and 110th Congresses, we show that members of Congress are more extreme than their constituents, i.e., that there is a lack of congruence between American voters and members of Congress. We also show that when a congressional legislator is replaced by a new member of the opposite party, one relative extremist is replaced by an opposing extremist. We call this leapfrog representation, a form of representation that leaves moderates with a dearth of representation in Congress. We see evidence of leapfrog representation in states and House districts and in the aggregate as well: the median member of the 109th House was too conservative compared to the median American voter, yet the median of the 110th House was too liberal. Thus, the median American voter was leapfrogged when the 109th House transitioned to the 110th. Although turnover between the 109th and 110th Senates occurred at approximately the same rate as between the 109th and 110th Houses, the Senate appears to be a more moderate institution whose median member does not move as abruptly as that of the House.


c1 Joseph Bafumi is Assistant Professor of Government, Dartmouth College, 6108 Silsby Hall, Hanover, NH 03755 (

c2 Michael C. Herron is Professor of Government, Dartmouth College, 6108 Silsby Hall, Hanover, NH 03755 (


An earlier version of this article was presented at the 2007 Annual Meeting of the Midwest Political Science Association, Chicago, Il. The authors thank John Carey, Ken Benoit, and seminar participants at Columbia University, Dartmouth College, Duke University, Harvard University, Princeton University, Stanford University, and Yale University for comments; Ben Goodrich for research assistance; the Nelson A. Rockefeller Center at Dartmouth College for financial support; and Stephen Ansolabehere and Gary Jacobson for sharing data.