WASHINGTON — Angus King of Maine, who ran as an independent for the US Senate, said Wednesday he would caucus with Democrats, giving the party a 55-45 majority.
King’s decision was widely expected, but the former two-term governor maintained that he would not be bound by partisanship and would remain an independent voice for his state.
“By associating myself with one side, I am not in automatic opposition to the other,” King said outside the Senate floor. “No one party can control the outcome of our collective deliberations.”
Senator Harry Reid of Nevada, the majority leader, later joined King to welcome him into the caucus, saying that he hoped King “will be a bridge to working with the Republicans.”
Afterward, the two strode into a hall for an organizing caucus. King is one of a dozen new members of the upper chamber of Congress, most Democrats, including Elizabeth Warren of Massachusetts.
King will take the seat being vacated by Senator Olympia Snowe, one of the few Republican moderates in chamber. He arrives in a Washington deeply divided by ideology, amid wide differences over tax policy, spending, and a host of other issues that could continue partisan gridlock on Capitol Hill.
On the campaign trail, King had declined to say which caucus he would join. But it was widely expected he would join the Democratic caucus, which currently has two independents among its ranks. Senator Bernie Sanders, a liberal from Vermont, was easily reelected and will again join the caucus. Retiring Senator Joe Lieberman of Connecticut served as an independent in his final term, after a long career as a Democrat.
King said he relied on the advice of Lieberman and Sanders before announcing his decision. He spoke with Lieberman for 20 minutes over the phone.
Asked about King Wednesday, Lieberman said: “We need more independents. ... You don’t have to toe the line.”
Last week’s election made it easy to choose sides, King said, alluding to the wider advantage the Senate Democrats will have — the party picked up two more seats — when the new session of Congress begins in January.
“Where one party has a clear majority and effectiveness is an important criterion, affiliating with the majority makes the most sense,’’ he said. “The majority has more committee slots to fill, has more control over what bills get considered, and more control over the Senate schedule.
“In answering this question repeatedly during the campaign,” King said, “I established two basic criteria — that I wanted to maintain my independence as long and as thoroughly as possible while at the same time being effective in my representation of Maine.”
King said he thought about going at it alone, but ruled that out because he would be largely excluded from the crucial work in committees. “Occasionally, my vote would prove crucial and be eagerly sought by both sides, but in the long run, I would be relegated to the sidelines as the day-to-day work of the Senate was done by others.”
King got no overtures from Senate minority leader Mitch McConnell to join the Republican caucus, but did meet with Roy Blunt and Susan Collins.
Republican-aligned groups spent $3.7 million in a losing attempt to defeat King. The National Republican Senatorial Committee dumped $1.3 million, while Crossroads GPS spent about $1 million.
King hopes for a seat on the Finance Committee, but acknowledged it is a long shot to get a spot on the coveted panel.Bobby Caina Calvan can be reached at bobby.calvan@
globe.com. Follow him on twitter@GlobeCalvan.