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Editorial boards and campaign ad watchdog groups called the commercial misleading, but coverage of the ad reached an incredibly diverse audience, including pop culture Web sites such as MTV and TMZ.com.

Mr. Obama said Thursday that Mr. McCain is demeaning the election.

“So far, all we’ve been hearing about is Paris Hilton and Britney Spears. I mean, I do, I do have to ask my opponent, is that the best you can come up with? Is that really what this election’s about? Is that what is worthy of the American people?” he said in Cedar Rapids, Iowa.

The Democrat sent a fundraising e-mail asking supporters to give money to help counter Mr. McCain’s commercial. His campaign also announced a new Web site to catalog Mr. McCain’s negative attacks.

On Wednesday, Mr. Obama was far more pointed, twice suggesting that Republicans were operating a stealth campaign about race.

“Nobody really thinks that Bush or McCain have a real answer for the challenges we face, so what they’re going to try to do is make you scared of me: You know, he’s not patriotic enough. He’s got a funny name. You know, he doesn’t look like all those other presidents on those dollar bills, you know. He’s risky. That’s essentially the argument they’re making.”

McCain campaign manager Rick Davis said that amounted to playing “the race card, and he played it from the bottom of the deck.” Mr. McCain concurred.

“I agree with it, and I’m disappointed that Senator Obama would say the things he’s saying,” Mr. McCain told reporters in Racine, Wis. He told his town hall audience that he was proud of the celebrity ad.

In his conference call with reporters, Mr. Plouffe was asked twice to point out where Mr. Bush or Mr. McCain had said the Democrat didn’t look like American presidents. Mr. Plouffe did not give a direct answer, but said Mr. Obama didn’t intend to raise the issue of race.