(AP) - Barack Obama stepped triumphantly into history Wednesday night, the first black American to win a major party presidential nomination, as thousands of Democrats transformed their convention hall into a joyful, shouting celebration.

Former rival Hillary Rodham Clinton asked delegates to the partyconvention to make their verdict unanimous "in the spirit ofunity, with the goal of victory." And they did, with a roar.

Competing chants of "Obama" and "Yes we can" surged up fromthe convention floor as the outcome of a carefully scripted rollcall of the states was announced.

Obama, the son of a black Kenyan father and a white Americanmother, is now one victory from becoming president of a nationwhere, just decades ago, many blacks were denied the vote.

But even as he won the nomination, there was open talk in theconvention city that Obama's race remained a stumbling block towinning the White House.

"A lot of white workers ... and quite frankly a lot of unionmembers believe he's the wrong race," AFL-CIO Secretary-TreasurerRichard Trumka told a breakfast meeting of Michigan delegates.

In the general election, Obama will face Republican Sen. JohnMcCain of Arizona, who will accept his party's nomination next weekin St. Paul, Minn.

The polls showed a close race ahead with McCain, a formerVietnam prisoner of war a few days shy of his 72nd birthday, andObama was hoping Democrats would leave their convention uniteddespite the hard feelings remaining from a bruising primarycampaign that stretched over 18 months.

Former President Bill Clinton did his part, delivering a strongpitch for the man who outmaneuvered his wife for the nomination."Everything I've learned in eight years as president and the workI've done since, in America and across the globe, has convinced methat Barack Obama is the man for this job," he said, to loudcheers.

Michelle Obama, watching from her seat in the balcony, stood andapplauded as the former president praised her man.

The convention ends Thursday with Obama's acceptance speech, anevent expected to draw a crowd of 75,000 at a nearby footballstadium where an elaborate backdrop was under construction.

After Obama's nomination, delegates filled out his ticket a fewhours later, naming Delaware Sen. Joseph Biden vice presidentialrunning mate, also by acclamation.

Addressing the convention, Biden said Obama was right aboutIraq, a war he opposed from the start, and McCain was wrong.

"These times require more than a good soldier. They require awise leader," Biden said. "A leader who can deliver change. Thechange that everybody knows we need."

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