Sen. Olympia Snowe (R-Maine), one of the Senate's only true centrist Republicans, caused "nothing short of a political earthquake" on Tuesday by announcing that she won't seek re-election this fall. Snowe, a strong favorite to win a fourth term, says she can no longer be productive amid the "atmosphere of polarization and 'my way or the highway' ideologies" in Washington. Snowe's departure plans caught everybody off-guard, especially her Republican colleagues, who have been working hard to seize control of the Senate. Democrats, with a slender 53-47 majority, have a much higher number of open and competitive seats to defend this fall than Republicans do — and now they have a prime chance to pick up a Republican seat in blue Maine. How much will Snowe's retirement hurt the GOP?

The GOP can forget about taking the Senate: Snowe just handed a "huge gift to Democrats," and dealt a huge blow to Republicans, says Steve Kornacki at Salon. The race to replace Snowe "is not a gimme for Democrats," especially if a third-party candidate jumps in. "But it's very, very winnable" given Maine's liberal bent and the Democratic Party's stronger statewide candidates. And if Snowe's seat goes to a Democrat, that "alters the playing field nationally," making it awfully tough for Republicans to win the Senate.
"Olympia Snowe's huge gift to Democrats"

Actually, this gives Republicans a fighting chance: "By retiring, [Snowe] is actually doing the GOP a favor," says John Cole at Balloon Juice. Snowe was facing a primary challenge from a Tea Party insurgent who just might have beaten her in a GOP primary, but would have almost certainly lost in November. "Now, at least, there is a sliver of a chance the GOP may find someone... who does not have her unpopular record as a 'moderate' and will stand a better chance in the general."
"She's actually doing them a favor"

Democrats may win, but the country loses: Snowe's seat will probably "easily be taken by a Democrat," says Cassie Murdoch at Jezebel. But what's good news for Democrats is a bad sign "for the future of our democracy." If a reasonable, seasoned, aisle-crossing, moderate senator like Snowe "can't handle this partisan bullshit anymore," the remaining "civilized members of Congress" can't be far behind. "Way to abandon us in our time of need," Snowe.
"Snowe retires because she's had enough of this partisan bullshit"