Why Party Polarization Affects Presidential Success Differently in the Senate and House: Testing for Conditional Effects of Party Control and Presidential Approval

Abstract

This paper reports a logit analysis of over 8500 conflictual House and Senate roll calls from 1953-2012. We test for conditional effects of party control, party polarization, and presidential approval in separate models for the House and Senate. Our analysis replicates the substantive findings of previous research regarding the effects of party control and polarization:• In House, rising party polarization increases the probability of winning for majority presidents and decreases the probability of minority presidents. • In the Senate, rising party polarization suppresses the probability of winning for both majority and minority presidents.• Rising party polarization and the emergence of the “minority party filibuster” account for different relationships in the Senate. When cloture votes are excluded from the analysis, the effects of party control are similar to those in the House — as party polarization increases, the probability of winning increases for majority presidents and decreases for minority presidents, though the slopes are less steep than in the House.The conditional effects approval on success are less consistent than the effects of party:• In the House, only majority presidents benefit from high public approval — rising approval increases the probability of winning for majority presidents and decreases the probability of minority presidents. • In the Senate, we find the same effects for approval — rising approval increases the probability of winning for majority presidents and decreases the probability for minority presidents, but the negative slope for minority presidents is less steep than in the House.• Basic presidential-congressional relations theory does not anticipate negative effects for approval. We can only speculate why this occurs, but since we find similar relationships in both chambers, future research should explore this further.