James King, a lawyer who lives in Dover, told The Republican newspaper of Springfield on Wednesday that he's ending his campaign and will support Warren.
King's campaign was unable to gain much traction as Warren, a Harvard Law School professor and consumer advocate, emerged as the likely Democrat to challenge Republican Sen. Scott Brown in November.
A spokesman for King did not immediately return a message.
Marissa DeFranco, an immigration attorney from Middleton, remains in the race but would need at least 15 percent support at the Democratic State Convention in June to qualify for the September primary ballot.
Copyright 2012 The Associated Press.
