Party Unity, Ideology, and Polarization in Primary Elections for the House of Representatives: 1956-2012

Increasing party polarization in Congress is a vexing phenomenon for political scientists, as it offers a theoretical conundrum. Members of Congress have become increasingly ideologically divided by party in recent years, which seems counterintuitive as the public electorally punishes representatives for excessive partisanship and ideological behavior. One explanation for this result is that members receive benefits for such behavior during primaries. This article examines the effect of ideological and partisan behavior on primary challenges and primary vote totals for incumbent House members. The results show that incumbents receive benefits in the primary from greater levels of partisanship but not greater levels of ideological extremity. This finding is substantively important as it provides further insight into the motivation of congressional incumbents and offers a partial explanation for the rise in congressional polarization.