Former Gov. Angus King has won the Senate race in Maine, running as an independent. King will take over the seat held by retiring Republican Sen. Olympia Snowe. Another independent, Vermont's Sen. Bernie Sanders, also has been re-elected.
Four Democrats senators have also won re-election: Bill Nelson in Florida, Sheldon Whitehouse in Rhode Island, Ben Cardin in Maryland and Tom Carper in Delaware. Republican Sen. Bob Corker was re-elected in Tennessee.
King hasn't said which party he will caucus with, but Republican groups have spent millions of dollars opposing his candidacy.
Democrats now control the Senate 53-47, including the two independents who caucus with them, Sanders and retiring independent Sen. Joe Lieberman of Connecticut.