Philadelphia ? Sen. Barack Obama was endorsed Wednesday by a labor union and two Democratic superdelegates as a poll showed he has cut Sen. Hillary Rodham Clinton’s lead in Pennsylvania almost in half since mid-February as he strives to deny her a resounding victory in the state’s presidential primary.

The Illinois senator peeled off an affiliate of the American Federation of State, County and Municipal Employees, which has endorsed Clinton. The Philadelphia-based local of the National Union of Hospital and Health Care Employees has about 16,000 members.

Its president, Henry Nicholas, announced the endorsement while introducing Obama at a meeting of the Pennsylvania AFL-CIO.

Nicholas, who also is president of the 150,000-member national union and an AFSCME international vice president, said he took the step “because justice told me it was the right position to take.”

Meanwhile, superdelegates Wyoming Gov. Dave Freudenthal and former Montana Sen. John Melcher endorsed Obama, as did former Indiana Rep. Lee Hamilton, who served as chairman of the Foreign Affairs and Intelligence committees and was vice chairman of the Sept. 11 commission. Hamilton’s endorsement could boost Obama’s national security standing.