The only Democrat to buck his party during Monday's Senate vote on the "Buffett Rule" was Sen. Mark Pryor, D-Ark., a moderate Democrat not up for reelection this year. But in 2014, Pryor's name will be on the ballot if he wants another term -- and his vote is the latest reminder that senators up for reelection next cycle are already gearing up.
In Montana, Democratic Sen. Max Baucus has already aired a radio ad. There are rumors that outgoing Gov. Brian Schweitzer , a popular figure, could challenge him in a primary. Baucus is taking no chances.
In Kentucky, Senate Minority Leader Mitch McConnell, R-Ky., has built a $5 million war chest. He raised more than $1 million in the first quarter of this year and his campaign has looked to the 2010 reelection campaign of Senate Majority Leader Harry Reid as a measuring post.
In addition to Pryor, who was the second most conservative Democratic senator in 2011 according to National Journal's vote ratings, there are some other moderate Democrats that could face potentially tough races. Sens. Mary Landrieu, D-La., (7th most conservative Democrat), Jeanne Shaheen (11th most conservative Democrat) and Mark Begich, D-Alaska, (12th most conservative Democrat) are each up for reelection as well.