BOSTON Senator Olympia Snowe, one of the few remaining Republican moderates in Congress, announced on Tuesday that she will not seek re-election for a fourth six-year term, citing the attitude of toxic partisanship in Congress.
In a statement, Snowe said she was in good health and had "no doubt" she would have won re-election in November.
Snowe said she was "well prepared for the electoral battle" she would have faced - one that analysts think could come from the conservative wing of her own party.
"I do not realistically expect the partisanship of recent years in the Senate to change over the short term," Snowe said. "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."
Her decision complicates Republican efforts to win control of the Senate from President Barack Obama's Democrats in the November 6 election.
Maine's junior U.S. Senator, Susan Collins, is another moderate Republican.
"I am absolutely devastated to learn that Olympia has decided not to seek re-election," Collins said in a statement. Olympia could always be counted on as a leader who sought solutions, not political advantage."
Snowe has racked up many firsts during a legislative career that included stints in Maine's House and Senate and eight terms in the U.S. House of Representatives before she was elected to the U.S. Senate in 1994.
The first Greek-American woman to serve in the House and Senate, the hard-working legislator has rarely missed a roll call vote in her career.
Snowe was listed by Time magazine as one of America's 10 best senators in 2006. She was cited for effective work on behalf of Maine's residents and the ability to set aside partisanship. That year, she won re-election in a 74-21 percent landslide.
In 2009 Snowe angered many in her party by being the only Republican to vote for Obama's signature healthcare reform bill in the Senate Finance Committee, saying she believed the process should move forward. However, she voted against the bill when it came before the full Senate.
Over the years conservative groups, appalled by Snowe's support of legalized abortion, environmental protections, stem cell research and gay rights, have branded her a "RINO" -- a Republican in Name Only.
(Additional reporting by Thomas Ferraro, Rick Cowan and Donna Smith. Editing by Christopher Wilson)