In pursuit of power: Competition for majority status and Senate partisanship

During the 20th century, Congress experienced two main shifts in partisan conflict. Early decades were marked by a substantial decrease in party divisiveness, reaching a nadir by mid-century. Beginning in the 1970s, partisanship has increased to the point that Congress is viewed as “hyper-partisan.” Political scientists have thoroughly examined this more recent shift; however, few studies consider why party divisiveness has fluctuated during the past century and over time more generally. Lee’s recent work contends a main factor that drives legislative partisanship is the majority party’s prospects for retaining control of its chamber. Using data on every Senate roll call vote since 1915 and a novel measure of party competition, I test an extension of Lee’s argument and examine whether partisan voting is associated with insecure majority status. My results indicate that voting coalitions in the Senate become more partisan as the majority’s probability of remaining in power decreases.