Former Maine gubernatorial candidate Eliot Cutler endorsed his fellow independent Monday night, saying King brings "the reputation and the disposition that will make him a great senator."

Sen. Snowe, a 33-year veteran of Congress, announced she would not seek re-election last week because she was frustrated with the partisanship in Washington.

"It is time for change in the way we govern, and I believe there are unique opportunities to build support for that change from outside the United States Senate. I intend to help give voice to my fellow citizens who believe, as I do, that we must return to an era of civility in government driven by a common purpose to fulfill the promise that is unique to America," she said.

The Associated Press contributed to this report.