Logrolling for a leg up: presidential elections and power in the US Senate

Abstract

Legislators may choose to vote similarly in roll call votes for many reasons. The primary reason would be that the legislators have similar ideologies. Public choice economics finds evidence of log-rolling behaviour, where politicians support each other in exchange for votes. However, another theory is plausible. It is possible that when a fellow legislator has a chance at taking a higher office, some legislators will vote with that politician in hopes of being rewarded if that politician reaches office, either in political favours or direct promotion to an appointed position. I use data from the 110th US Senate (2007-2008) to investigate this theory. During this period, three Senators had significant chances of winning the presidential election. By pairing roll-call voting data to predicted election probabilities, I expand the spatial econometric political model (Chupp 2014) to estimate the impacts of election probability on power measures for the three candidates.