Former Maine Governor Angus King, an independent, will announce his intent to run for Olympia Snowe’s seat in the Senate, further throwing up the chess board in a race that a week ago was thought to be securely in Republican hands. Now, a case can be made that either party or even independent King will take the seat.

A run by King as an independent for the seat being vacated by GOP Sen. Olympia Snowe of Maine is sparking fears among some Democrats that the socially liberal former two-term governor could siphon off enough votes from a Democratic Senate nominee to throw the election to the GOP candidate.

King said that doesn’t worry him.

“I don’t go into campaigns planning to be a spoiler,” King said in the phone interview. “When I go into a campaign I go in planning to win.”

King was a Democrat before switching to an independent before winning the Governor’s mansion. He’s a longtime friend of Chellie Pingree, the Maine Congresswoman who is running for the seat on the Democratic side. He has apparently donated at least $3,000 to President Obama’s campaigns since 2008.

Yet he would not say which party he would caucus with in the Senate, which was something that helped undo Charlie Crist’s independent bid for Senate in 2010. Even if he did announce that he would caucus with the Democrats, you would effectively have two Democrats and one Republican in the race at that point, and the nature of our first-past-the-post election system suggests that this would favor the Republican.

Pingree and former Governor John Baldacci are competing for the Democratic nomination. On the Republican side, Attorney General Bill Schneider and former Senate President Rick Bennett will run, with Secretary of State Charles Summers and State Treasurer Bruce Poliquin considering (AG, Secretary of State and Treasurer are all appointed positions in Maine). So you have the possibility of an election campaign for one seat featuring two ex-Governors, a Congresswoman, and three Constitutional officers. I guess opportunities like this don’t come along so often in Maine.