Former Maine governor Angus King, an independent, won the open Maine Senate race Tuesday, beating back a challenge from Republican Secretary of State Charlie Summers, according to AP.

Even though no vote totals have been reported, AP has called the race for King. The Washington Post has not yet called the race.

(Robert F. Bukaty/Associated Press)

Now that King has been elected to the Senate, questions will persist about whether he will caucus with Democrats. Despite steadfastly refusing to pick a party to caucus with during the campaign, national Democrats and Democratic-leaning outside groups dumped millions into the race to ward off Summers when the polls narrowed.

National Democrats never embraced their nominee, state Sen. Cynthia Dill, in this race, instead apparently banking on King caucusing with them.

King will replace retiring Sen. Olympia Snowe, a moderate-leaning Republican.

With Sen. Joe Lieberman (I-Conn.) retiring, King's win means the Senate will continue to have two independents out of 100 members. The other is Sen. Bernie Sanders (I-Vt.), who caucuses with Democrats and was set to be reelected on Tuesday.