Angus King will become the 55th member of the U.S. Senate’s Democratic caucus when he is sworn into his new job in January, Maine’s senator-elect said Wednesday at a news conference in the U.S. Capitol.

The decision — while largely expected — puts an end to months of speculation about which party King, an independent former governor, would team up with when he arrived in Washington, D.C. The decision also helps Democrats add to their newly expanded Senate majority following last week’s elections.

King said joining the Democratic caucus will still allow him to stake out independent positions. It also positions him well to be an effective senator, he said, since the Democrats are the Senate’s majority party.

“I have decided to affiliate with the Democratic caucus because doing so will allow me to take independent positions on issues as they arise and at the same time be an effective representative of the people of Maine,” he said in prepared remarks. But, he added, “by associating myself with one side, I am not in automatic opposition to the other.”

Although King was the front-runner from the time he joined the race to replace Olympia Snowe, who is retiring from the Senate, he previously had refused to say whether he would caucus with Senate Democrats or Republicans, or any party at all. He said Wednesday it became clear he would have to caucus with one side or the other to secure assignments on committees, which is where the Senate does the bulk of its work.

If he didn’t join a caucus, King said, “it would severely compromise my effectiveness on behalf of Maine.”

The Senate currently has two independent members, Bernie Sanders of Vermont and Joseph Lieberman of Connecticut, and both caucus with the chamber’s Democrats. With Lieberman leaving the Senate at the end of the year, King and Sanders will be the only independents in the chamber.

In his prepared remarks, King said he consulted closely with Sanders and Lieberman about their experience as independent members before choosing to caucus with Senate Democrats.

“Both confirmed that the Democratic caucus generally and its leadership in particular had consistently allowed them to maintain their independent positions and had never forced positions upon them in the name of party loyalty,” King said.

He also spoke with Senate Majority Leader Harry Reid of Nevada and a former Senate majority leader, George Mitchell of Maine, before making his caucus pick.

“I came away from these conversations reassured that my independence would be respected, and no party line commitment would be required or expected,” he said.

Reid joined King at his news conference to welcome Maine’s incoming junior senator to the Democratic caucus.

“I embrace [King’s] independence. We as a caucus embrace that independence,” he said. “I’m confident that Sen. King will be a bridge to working with Republicans.”

King and Reid discussed committee assignments for Maine’s new senator as part of multiple conversations about his joining the Democrats, said King spokeswoman Crystal Canney.

“The committee assignments are still being worked through, and he feels very positive about them,” Canney said.

King planned to cast a vote for Reid as Senate majority leader in Wednesday’s leadership elections.

King also discussed committee assignments with Maine’s soon-to-be senior senator, Republican Susan Collins, when the two met in Collins’ Washington, D.C., office Tuesday.

Collins said in a statement that she was disappointed, but not surprised, by King’s decision to go with the Democrats.

“I am certain that we will work closely together to address the challenges facing Maine and our nation,” she said. “I look forward to having him as a colleague.”

More than his choice of party, what’s critical is that King “has made clear his intention to work with colleagues on both sides of the aisle in an attempt to build consensus and break the partisan gridlock that has enveloped Congress for too long,” Snowe said in a prepared statement, “and that is precisely what Americans are clamoring for in Washington.”

Before settling on the Democratic caucus, King said he spoke with more than a dozen senators from both parties. Those conversations included one with Sen. Roy Blunt, R-Mo., vice chairman of the Senate Republican Conference.

Blunt and King met for about 45 minutes to discuss the possibility of King joining the Senate Republican caucus, Canney said. “It was a good conversation.”

King never spoke with the Senate Republican leader, Mitch McConnell of Kentucky, Canney said.

Representatives for Blunt and McConnell didn’t immediately respond to requests for comment.