Republicans set their sights on three Democratic-held seats — Nebraska, North Dakota and Virginia. Republican candidates in those states grabbed the early lead.

King prevailed over Republican Charlie Summers and Democrat Cynthia Dill in the race to replace Republican Sen. Olympia Snowe, who blamed partisan gridlock in Washington for her unexpected decision to retire after 18 years in the Senate. The Associated Press called the race based on interviews with voters as they left polling stations.

In Ohio, Democratic Sen. Sherrod Brown survived an onslaught of outside spending, some $30 million, to defeat state treasurer Josh Mandel. In Pennsylvania, Democratic Sen. Bob Casey survived a late scare from businessman Tom Smith, who invested more than $17 million of his money.

Democratic Rep. Chris Murphy won the Connecticut Senate seat held by Sen. Joe Lieberman, the independent who was the Democratic Party’s vice-presidential nominee in 2000. Murphy’s win marked the second straight defeat for former wrestling executive Linda McMahon, who spent $50 million of her own wealth in a failed effort against Sen. Richard Blumenthal in 2010 and more than $42 million this election cycle.

Texas sent tea party-backed Ted Cruz to the Senate as the Republican won the seat held by retiring Republican Sen. Kay Bailey Hutchison.

In Florida, Democratic Sen. Bill Nelson triumphed in his bid for a third term, holding off a challenge from Republican Rep. Connie Mack. Republican groups had spent heavily against Nelson early in the race, but the moderate Democrat was a prolific fundraiser with wide appeal among Democrats and some Republicans in the Panhandle.

Independent Sen. Bernie Sanders won a second term in Vermont. Democratic Sens. Sheldon Whitehouse in Rhode Island, Ben Cardin in Maryland and Tom Carper in Delaware were all re-elected. Cruising to another term were Democratic Sens. Debbie Stabenow in Michigan, Kirsten Gillibrand in New York, Bob Menendez in New Jersey and Amy Klobuchar in Minnesota.

In West Virginia, Democratic Sen. Joe Manchin won a full term even though his state went heavily for Republican presidential nominee Mitt Romney.

Tennesseans gave Republican Sen. Bob Corker a second term. Wyoming voters did the same for Sen. John Barrasso, and Republican Roger Wicker captured another term in Mississippi.

King has resolutely refused to say which party he’d side with if elected, and the outcome of the presidential election and the final Senate lineup could influence his decision. Members of both parties have indicated that they expect King — former governor and one-time Democrat who supports President Obama — to align with Democrats. One factor could be the million-plus dollars that Republican-leaning groups such as the U.S. Chamber of Commerce and Karl Rove’s organization spent on ads criticizing King.

Democrats currently hold a 53-47 edge in the Senate, including the two independents who caucus with them. Republicans need a net of four seats to grab the majority, three if Republican Mitt Romney wins the presidency.