Hayward, Matthew2011-07-192011-07-192011-07-19https://hdl.handle.net/11299/109495Senate elections affect senators’ partisan behavior. Senators encounter incentives to display party loyalty, but they must win reelection every six years to continue pursuing ideological, partisan, and career-based goals in the U.S. Senate. Since most senators desire reelection, they respond to credible electoral threats. Therefore, a senator’s electoral vulnerability affects his party loyalty. In this thesis, I examine the effect of elections on senators’ party loyalty through interviews with Senate staffers, analysis of senators’ roll-call voting, and studies of four senators’ careers. I conclude that senators facing competitive elections display less party loyalty toward the end of their terms relative to their colleagues. I also find that the effect of elections on senators’ party loyalty during the last two years of a Senate term parallel the effect of elections on the party loyalty on House incumbents seeking reelection. Overall, senators’ perceptions of electoral vulnerability influence how they represent their constituents.en-USSumma Cum LaudePolitical ScienceCollege of Liberal ArtsThesis or Dissertation