In an unusually candid interview, a top official for the largest union backing Obama said that internal union polling shows that the race remains much more volatile and fluid in key battleground states than public polling suggests. He warned that low-information swing-state voters are saying they still don't have a firm enough grasp on Obama's life-story, character and record for the Illinois Senator to close the deal with them.

The comments by the official, AFL-CIO deputy political director Mike Podhorzer, are surprisingly frank and seemed intended as a reality check at a time when polls show the momentum has clearly swung in Obama's favor.

"This election remains extremely volatile in the battlegrounds," Podhorzer told us. "The public polls are giving a false sense of precision about where the race is. That's a story that's not really being told."

Strikingly, Podhorzer said that his union's internal polls -- which push voters hard on the question of whether people are really firmly committed to their pick -- show that as many as "15 to 20 percent" of battleground state voters remain "persuadable," as he put it, despite what public polls say about the level of undecided voters.

"There are more voters than you'd expect who are just starting to pay attention to the election," he said. "And there's a lot of room for people to go back and forth."

Podhorzer stressed that he is impressed by Obama's gains and is convinced Obama is on track to win right now. But he said that the union's interaction with battleground-state voters, combined with extensive internal polling, indicate that this dynamic is anything but fixed and that there's much more fluidity than is generally acknowledged.

Podhorzer ascribed the fluidity to two factors: The uncertain and rapidly shifting political landscape created by the financial crisis, and the relatively little time Obama has spent as a politician in the national spotlight.

"Low information voters who haven't been following this don't know very much about Obama, in a way that might be different from other elections," he said. "Voters are saying, `I really don't want another four years of this, but I don't know much about him."

"One of the things we find is that there's no sense of where he came from, what he's achieved, and that he's had to work hard for what he's done," Podhorzer continued. "People have much less of a grasp on Obama's biography than they do of McCain, who has created a persona of POW, survivor, independent, fought honorably for his country."

To be sure, union officials also see the vacuum in voter knowledge as a big opportunity. The union has launched a massive campaign in the swing states to educate voters about what McCain's policies would mean for them in the real world and how Obama is much more in touch with their problems than McCain is. And the polling shows that these voters are very receptive to this argument, Podhorzer says.

"When we lay out McCain's economic policies, like taxing health care benefits and privatizing social security, these voters abandon him readily," he said. "That's not what people assume McCain is about."

But Podhorzer cautioned against complacency. "Obama has definitely pulled ahead of McCain, but there's softness," he said. "With the financial crisis, and with surprises we can't imagine yet, there's a lot of work to do."