In a surprising boost for Senator Barack Obama, the International Brotherhood of Teamsters endorsed him on Wednesday, giving him new momentum among a group where he is eager to shore up support: blue-collar men.
James P. Hoffa, the president of the Teamsters, which represents more than 1.2 million truck drivers, warehouse employees and other workers, announced the endorsement after meeting with Mr. Obama in Austin, Tex.
“Senator Obama understands the challenges working people face every day,” Mr. Hoffa said. “He is the candidate in the best position to lead our movement to restore the American dream for working people in this country.”
A spokesman said Mr. Hoffa would campaign with Mr. Obama on Friday in Ohio, where the Teamsters have considerable strength.
Teamster officials said the union’s board had voted to endorse Mr. Obama, who is seeking the Democratic presidential nomination, after a weeklong scientific survey of the union’s rank and file found strong support for him.
With the Teamsters’ move, labor leaders said, Change to Win, a five-million-member coalition of unions that broke away from the A.F.L.-C.I.O., is expected to vote Thursday to endorse Mr. Obama.