Campaign spending and the top-two primary: How challengers earn more votes per dollar in one-party contests

Abstract

The top-two primary system changes the typical two-stage electoral process by creating scenarios in which two candidates from the same party may face each other in the general election. In two-party contests, voters receive information from candidate party labels and from campaign outreach, which is facilitated by campaign expenditures. Combined, this information helps voters make decisions on Election Day. In the absence of differentiating party labels in one-party contests, the information provided by candidate spending should matter more. Specifically, I argue that expenditures made by challengers facing same-party opponents should be more effective for increasing vote share than expenditures made by those facing opposite-party opponents. This study examines state legislative elections in California and Washington to investigate how the effectiveness of challenger campaign expenditures is conditioned by the presence of either a one-party or two-party contest. Results find that as challengers in one-party contests spend more, they are able to increase their vote share at more than double the pace per dollar spent when compared to challengers in two-party contests. Findings complement a broad literature investigating the role of electoral institutions in shaping voter and candidate behavior.