Washington, D.C. ? The United Transportation Union on Tuesday endorsed Sen. Hillary Rodham Clinton for the Democratic nomination for president, the first national union endorsement of the 2008 campaign.

“The UTU has a long history of picking winners early. Hillary will be a president that America’s working families can count on. Time and again, as a United States senator, she has stood with us,” UTU President Paul Thompson said in a statement.

Clinton is leading in national polls for the Democratic nomination. She said that she was honored to get the endorsement.

“America’s workers have been invisible to this administration, and it’s time they had an advocate in the White House,” said the New York senator.

The UTU, which calls itself the largest railroad operating union in North America, represents 125,000 active and retired members in the railroad, bus and public transit industries.