Dynamic Responsiveness in the US Senate.

Using simple formal theories of two-party competition in a single dimension, I develop a theory of dynamic responsiveness. This theory suggests that parties react to past elections in the following way: winning parties choose candidates that are more extreme and losing parties choose candidates that are more moderate. Moreover, the size of past victories matters. Close elections yield little change, but landslides yield large changes in the candidates offered by both parties. I test this theory by analyzing the relationship between Republican vote share in US Senate elections and the ideology of candidates offered in the subsequent election. The results suggest that Republican (Democratic) victories in past elections yield candidates that are more (less) conservative in subsequent elections, and the effect is proportional to the margin of victory. This suggests that parties, candidates, and/or voters pay attention to past election returns and change their behavior in a way that privileges winning party candidates that are more extreme and losing party candidates that are more moderate in the next election. [ABSTRACT FROM AUTHOR]