The ideological component of Senate voting: Different principles or different principals?

Evidence exists on both sides of the question of whether or not legislator-specific, ideologically-driven shirking of constituent interest occurs. In this paper, we use a well-known model of such shirking by senators as our point of departure and add measures of inter-state constituent interests, the role of campaign contributions and, hence, the importance of whether or not senators are up for reelection. We find some evidence that the model provides a stronger explanation for senators up for reelection than for those who are not and that campaign contributions help determine voting decisions by these legislators. Finally, accounting for inter-state constituent interests, shirking is not a significant variable in the voting decisions of senators facing reelection. Thus, it appears that the reelection interests of some senators have been mistaken for ideologically-driven shirking.