"After an extraordinary amount of reflection and consideration, I am announcing today that I will not be a candidate for re-election to the United States Senate," Snowe said in a statement.
"After 33 years in the Congress this was not an easy decision. My husband and I are in good health. We have laid an exceptionally strong foundation for the campaign, and I have no doubt I would have won re-election. … I remain deeply passionate about public service, and I cherish the opportunity I have been given for nearly four decades to help improve the lives of my fellow Mainers.
"As I have long said, what motivates me is producing results for those who have entrusted me to be their voice and their champion. … 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. 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, which is what a fourth term would entail."
Snowe said she sees a "vital need" for a strong "political center" if democracy in America is to flourish.