DENVER -- So many of the political stars would seem to be aligned for the Democratic Party this year.

A wide majority of voters tell pollsters that the nation is on the wrong track. The Republican president has an approval rating that rivals Richard Nixon's just before his resignation.

Yet, as Sens. Barack Obama and John McCain prepare to formally accept their party's nominations, their competition appears rooted in a near deadlock.

"There are more undecided voters than ever before," Karen Ackerman, the political director of the AFL-CIO acknowledged yesterday. Many of them are union members in a year in which union leaders hope that a change in the party in the White House would add leverage to their stalled agenda on trade, health care, organizing rules and other issues.

"For us in the labor movement, this should be a no-brainer," Gerald McEntee, the president of AFSCME told thousands of union members and delegates here in the eve of the Democratic National Convention.

As the gavel is about to fall on the convention, several labor leaders were candid in confronting a difficult challenge they and the candidate they support face in trying to win the White House.

In a briefing for reporters, Ms Ackerman acknowledged that the union's challenge was heightened by attitudes toward their nominee's race.

"It's complicated, obviously, by the fact that there has never been an African-American candidate for president," she said.

Mr. McEntee put it more bluntly later in the afternoon at a labor rally in the Colorado Convention Center.

"They are going to say to so many of our white members in Appalachia, you can't vote for him, he's black," he thundered "We've got to say to them, 'That's bull.' Don't let them do this to us again, we should have learned our lesson."

Polls suggested that white working-class voters were a one of the tougher constituencies for Mr. Obama throughout his primary battle with Sen. Hillary Rodham Clinton. That demographic hurdle remains in his battle with Mr. McCain.

Rich Trumka, the secretary-treasurer of the AFL-CIO, was open in confronting that reality as he spoke near the end of an afternoon-long rally yesterday.

He described an encounter with "a woman I'd known for years," outside a Fayette County polling place before the Pennsylvania primary. He said she told him first that she would not vote for Mr. Obama because he was a Muslim. She cited the rumors that he would not wear a flag pin. Mr. Trumka said he told her neither was true. Then, he said, "her voice dropped a little bit and her eyes dropped down to the ground and she said, 'Because he's black."

"I said, 'Look around. Nemacolin's a dying town. There're no jobs here. Kids are moving away because there's no future here. And here's a man, Barack Obama, who's going to fight for people like us and you won't vote for him because of the color of his skin?

"Brothers and sisters, we can't tap dance around the fact that there are a lot of folks out there just like that woman. ...Those of us who know better can't afford to look the other way," Mr. Trumka said.

"We can't afford to shrug our shoulders; we can't afford to look away and we can't let those bigoted wisecracks to go unchallenged.

"That's why when we hear people say, 'America is not ready for a black president we have to get in their faces."

Mr. Obama's status as the first African-American nominee of a major party underscores his party's challenges in attracting white working-class votes. But the problem is not new with him. While he won a majority of the popular vote, exit surveys showed that former Vice President Al Gore trailed among white working-class voters by 17 percent. Four years later, Sen. John F. Kerry did still worse, trailing by 23 percent with that demographic group.