LITTLE ROCK, Ark. — Sen. Blanche Lincoln has fended off a union-backed challenger and anti-establishment sentiment to win a runoff for Arkansas' Democratic Senate nomination. Lincoln defeated union-backed Lt. Gov. Bill Halter on Tuesday. She'll face Republican congressman John Boozman in the Nov. 2 general election. Lincoln was considered among the country's most vulnerable senators, as groups to her right and left criticized votes on proposed changes to the national health care system.