Politico has called Sen. Kay Hagan one of the most vulnerable Democrats seeking re-election in 2014.
Larry Sabato of the University of Virginia agrees, and he offered the following explanation why:
Incumbency doesn’t mean much in Tar Heel Senate contests, which means that Sen. Kay Hagan (D) was always going to be vulnerable. As if to underline that, she occupies a seat in one of only two states (Indiana is the other) to switch back to the Republicans after supporting Barack Obama in 2008. House Speaker Thom Tillis (R) is a possible challenger, and the U.S. House delegation is overflowing with possible GOP opponents, too.
Rep. Renee Ellmers name is one of those possible Congressional challengers, and state Senate leader Phil Berger's name has also been rumored

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DON'T OVERLOOK PHIL BERGER FOR U.S. SENATE
November 29, 2012 - 5:23pm — eqvideriHang on folks, Thom Tillis hasn't actually yet won the 2014 Republican primary for U.S. Senate.
N.C. Senate leader Phil Berger is a serious contender -- smart, thoughtful, experienced, accomplished, conservative, and much better organized and more disciplined than Tillis.
He's not as gifted at gabbing, but in fact he raised more money than Tillis in 2012. And it's no accident that his staff of professionals has stayed out of the soap opera headlines.
Keep your eye on Phil Berger. He's already a leader, a veteran senator, and a strong fundraiser, well-prepared for the statewide stage. Hagan will be vulnerable, to say the least. And in an off-year election, Berger would be the more conservative Republican candidate, and likely to win the primary.
Most important, Phil Berger would serve North Carolina well in the U.S. Senate.