The Impact of Primaries on General Election Outcomes in the U.S. House and Senate

Theory: We draw on established theories concerning strategic politicians, political learning, and political campaigning to challenge the conventional wisdom that divisive primaries diminish a nominee's chances of winning the general election. We use the concept of "political Darwinism" and introduce three new types of variables that move beyond the unidimensional focus of the impact of primary vote margins on general election outcomes. Hypotheses: Primary vote margins have no independent impact on general election outcomes, instead, campaign spending in the primary, the mediating impact of time, and the size of the challenger pool are expected to have explanatory power. Methods: Regression analysis of all House and Senate incumbent elections from 1974-1988. Results: Challengers largely benefit from contested primaries. The challenger who survives a tough primary will be the best campaigner and will have benefitted from the publicity that such a victory may provide. Incumbents, on the other hand, are hurt by the occasional divisiveness that they might face. Furthermore, late primaries tend to strengthen the positive effects of primary elections for challengers and weaken the negative effects for incumbents.