WASHINGTON - Barack Obama all but erased Hillary Rodham Clinton's once-imposing lead among national convention superdelegates on Friday and won fresh labor backing as elements of the Democratic Party began coalescing around the Illinois senator for the fall campaign.

Obama picked up the backing of five superdelegates, including Rep. Donald Payne of New Jersey, a member of the Congressional Black Caucus who had been a Clinton supporter.

In addition, the American Federation of Government Employees announced its support for Obama. The union claims about 600,000 members who work in the federal and Washington, D.C., governments.

Obama, who won a convincing victory in the North Carolina primary and lost Indiana narrowly on Tuesday, has been steadily gaining strength in the days since.

Clinton also gained a superdelegate.

The developments left the former first lady with 271.5 superdelegates, to 268 for Obama. Little more than four months ago, on the eve of the primary season, she held a lead of 169-63.

In addition to Payne, Rep. Peter DeFazio of Oregon and two members of the Democratic National Committee from California announced they were supporting Obama.

"The election is over, everybody knows that. Obama has won," said Vernon Watkins, one of the two.

So, too, John Gage, president of the AFGE.

"Our people, I think, recognize the enthusiasm and vitality behind Senator Obama's campaign," he said in a statement.

"After careful consideration, I have reached the conclusion that Barack Obama can best bring about the change that our country so desperately wants and needs," said Payne, who in a statement said that Clinton is a good friend and he still holds her in high regard. Clinton's new supporter was Rep. Chris Carney, D-Pa. His congressional district voted overwhelmingly for the former first lady in the Pennsylvania primary on April 22.

Both Obama and Clinton have courted superdelegates in recent days in private meetings at party headquarters not far from the Capitol.

Despite Watkins' assessment, Clinton has shown no signs she is ready to quit the race. She is heavily favored to win Tuesday's primary in West Virginia, and is in the midst of a two-day swing through several other states with upcoming elections.

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Associated Press Writers Jesse Holland and Matthew Daly in Washington and Solvej Schou in Los Angeles contributed to this report.