The motion to invoke cloture on the treaty passed 67-28. There were no big surprises in terms of the supporters, as all of the ayes came from Senators who had stated their support for ratification, but it is still interesting to look at where the Republican support came from. Two of the ayes on cloture were from retiring members, Bennett and Voinovich, and four of the ayes came from Republicans running for re-election in 2012 (and two of these were Northeastern moderates, Brown and Snowe). Collins was the other moderate Northeasterner supporting cloture. Murkowski was another aye, and given her experience with the party this year it is no surprise that she would feel no obligation to follow the leadership on this issue. So seven of the eleven Republicans voting for cloture are either departing from the Senate or for various reasons are relatively weaker partisans than the rest of the caucus. Gregg did not cast a vote on cloture, but he is a likely yes vote on the treaty, and he is another outgoing member and a Northeastern Republican.

Notably, four of the ayes were Southerners: Isakson, Corker, Cochran, and Alexander. Corker and Alexander have obvious interests in making sure that the modernization deal goes through, since Oak Ridge would receive additional funding as a result, and Isakson and Corker have been considered a likely supporters of ratification since the committee vote. Cochran has been an unexpected, late addition to the pro-treaty side, but like Alexander he is not up for re-election until 2014, and he has had a relatively moderate voting record as measured by ACU ratings. The other seven were the most likely supporters of the treaty because of their weaker partisan attachments, retirements, or particular interest in the treaty (Lugar), but it is really these Southerners that helped clear the way for ratification. Corker potentially has the most to lose, as he is the only one of these Southern Republicans up for re-election in 2012, and he has been specifically targeted by the Heritage Foundation’s political action organization and threatened with a primary challenge backed by the National Republican Trust PAC. To his credit, it appears that Corker has completely ignored this pressure, and it is hard to see how support for arms control will fuel a backlash among primary voters, but of all the treaty supporters he is the most exposed to political risk.