Ideological Polarization and the Vanishing of Marginals: Retrospective Roll-Call Voting in the U.S. Congress

Abstract

The extensive literature on the recent ideological polarization in the U.S. Congress has not provided much in the way of incremental and member-specific explanations. I develop such a theory; I posit that members’ past electoral performance can influence their ideological extremity. This link requires a reexamination of congress members’ roll-call vote calculus. To do so, I adapt the theory of citizen retrospective voting to congress members’ roll-call voting. This new theory also provides a missing link in many studies of ideological shirking and democratic accountability. I test and confirm the theory of retrospective roll-call voting for the current period of ideological polarization, 1970 to 2008. As such, I argue that the recent trend of vanishing marginals has been a contributing cause in the recent trend of ideological polarization in the U.S. House.