One would think that having a 60 seat majority in the Senate would make it easier for the President to achieve his legislative goals. In my paper, I argue that this is only the case when members are not sure who the 60 Senators are. Exactly how would a Senator not know if he or she was part of the 60 seats?
I use the roll-call vote analysis of Poole and Rosenthal to construct an ideological model of the US Senate identifying individual Senator locations on the three occasions in the last 50 years when one party has attained a “filibuster proof” majority and also has control of the White House. On two of the three occasions, the 60th Senator has been surrounded by a group of other members who were statistically indistinct from each other. That meant that the President had multiple negotiating partners and did not have to win unanimity. Some might be members of the winning coalition while others might not.
On the other hand, the third case demonstrates the situation where the members are distinctly separate from each other. The only way the President wins is if he gets unanimous support from his side. It turns out getting unanimous support is an expensive proposition. The Senators understand the value of their position and will attempt to secure the most advantage. However, this advantaged position is not without its own costs to the Senator. Being known as the deciding vote has both its rewards and its perils.
In the end, the US does not have a parliamentary government. Analysis of voting blocs can only go so far. The US system is based upon the individual politician and ultimately analysis must be firmly rooted in the incentive structure of those individuals. My paper looks at individual motivations and then aggregates up those individual actions which collectively form the actual voting blocs revealed in roll call vote analysis.