Sen. Olympia Snowe, R-Maine, has announced she will not run for reelection, making it a lot less likely that Republicans will retain the Senate seat in a state that President Obama carried by 17 points in 2008.

"After an extraordinary amount of reflection and consideration, I am announcing today that I will not be a candidate for re-election," Snowe said in a statement, according to Roll Call.

The news will be greeted with a shrug in many conservative quarters, because she was a liberal Republican. But I have a much easier time tolerating such Republicans in states like Maine, where there's little hope that a true conservative can win a Senate seat. It's another story in a state like Utah, where there's no reason for conservatives to settle for anybody less than a principled conservative.

No doubt, Snowe was an obstacle to conservatives over the years. But she also took some important stands. If it weren't for her opposition, for instance, the Senate may well have been able to pass "card check" legislation, which would have made it a lot easier for unions to intimidate workers into choosing them. And though she voted for President Obama's health care law out of the Finance Committee, she pulled her support when it came up for a vote on the Senate floor, making it a lot more difficult for Democrats to pass and ensuring that Obama they would pay a higher political cost for ramming it through.

Snowe was popular in Maine and was seen as likely to retain her seat, according to Cook Political Report. Her decision not to run throws another monkey wrench into Republican plans to retake the Senate.