Snowe cites the partisan divide in Washington as a reason for retiring Washington (CNN) -- Republican Sen. Olympia Snowe of Maine announced Tuesday she will retire rather than seek re-election this year. Her statement cited the partisan divide. "I have no doubt I would have won re-election," Snowe said, describing her political service in Maine and Washington as "an indescribable honor and immeasurable privilege." While her motivation and sense of responsibility remain, she continued, "I do find it frustrating, however, that an atmosphere of polarization and 'my way or the highway' ideologies has become pervasive in campaigns and in our governing institutions." "Unfortunately, I do not realistically expect the partisanship of recent years in the Senate to change over the short term," Snowe said. So at this stage of my tenure in public service, I have concluded that I am not prepared to commit myself to an additional six years in the Senate. Initial reaction from Senate colleagues indicated Snowe's decision was unexpected. "I am absolutely devastated to learn that Olympia has decided not to seek re-election," said a statement by fellow Maine Sen. Susan Collins, also a moderate Republican. "I know this was an incredibly difficult decision for Olympia," said Collins, who lauded Snowe as "a leader who sought solutions, not political advantage." Democratic Sen. Chuck Schumer of New York expressed surprise at the news when told by CNN. "We'll miss her," Schumer said. She's a good, good lady and an example of ... sometimes how the roughness of the political world can affect things. She's great, and she'll be missed by people on both sides of the aisle. With Snowe in the race, two of the top political handicappers -- the Cook Political Report and the Rothenberg Political Report -- had considered the seat "safe Republican" in the November election. Democrats currently hold a 53-47 majority in the Senate but are defending 23 of the 33 seats up for grabs in November, including those of two independents who caucus with the Democrats. Guy Cecil, executive director of the Democratic Senatorial Campaign Committee, called Snowe's departure an "unexpected opportunity." "Maine is now a top pick-up opportunity for Senate Democrats," Cecil said in a statement. If there is one place in the country that is likely to reject the extreme, anti-middle class, divisive Republican agenda it is Maine. Democrats not only hold a strong registration advantage in the state, but this is a state that the president won by 17 points in 2008 and will likely win by a significant margin this year, as well. However, Texas Sen. John Cornyn, the chairman of the National Republican Senatorial Committee, said his party remains "well-positioned to win back a Senate majority in November." "Maine has a proud history of electing independent leaders, including a Republican governor in 2010, and while this will be a key battleground in the fall, I am confident it will remain in Republican hands," Cornyn said in a statement. Two Republican candidates already announced primary challenges to Snowe -- former Lisbon Falls Selectman Scott D'Amboise and Tea Party activist Andrew Ian Dodge. In addition, two Democrats being mentioned as potential candidates were businesswoman and 2010 gubernatorial candidate Rosa Scarcelli and state Rep. Emily Cain.