Mr. Obama ridiculed Mr. McCain for depicting him as a lightweight celebrity.
A day after the release of a McCain ad comparing Mr. Obama to Britney Spears and Paris Hilton, both campaigns veered away from the issues and into a squabble over who said what, who intended what and who insinuated the rest.
"Folks ought to just buckle up their seat belts," said Obama campaign manager David Plouffe, telling reporters on a conference call that they can expect more.
Mr. Plouffe announced a new Web site to catalog what he said were false attacks and distortions from Mr. McCain.
Hours earlier, the McCain campaign said Mr. Obama crossed the line of racial politics. Mr. Obama said Wednesday that President Bush and Mr. McCain attacked him as unworthy of the presidency because, as the Democrat put it, he doesn't "look like all those other presidents on those dollar bills."
A poll shows Mr. McCain has made up ground in the past month in three big swing states: Ohio, Florida and Pennsylvania.
The Quinnipiac University Poll put Mr. Obama ahead 46 percent to 44 percent in Ohio and Florida, and showed Mr. McCain narrowing a 12 percentage point gap in Pennsylvania to seven points, 49 percent to 42 percent.
"The $64,000 question is whether Senator John McCain´s surge is a result of Senator Obama´s much-publicized Middle Eastern and European trip, or just a coincidence that it occurred while Senator Obama was abroad," said Peter A. Brown, assistant director of the Quinnipiac University Polling Institute.
Mr. Brown said high gas prices have turned voters in favor of expanded offshore oil and gas drilling, a position Mr. McCain has embraced.
The tail end of the latest McCain ad takes a jab at Mr. Obama for opposing the expansion of oil drilling.
Mr. McCain's tone has become harsher after extensive media coverage of Mr. Obama's overseas trip and after changes within the campaign. In early July, Steve Schmidt, a veteran of Republican congressional campaigns and President Bush's 2004 re-election, was promoted to oversee day-to-day operations.
Mr. Schmidt on Wednesday alluded to the new McCain ad when he told reporters that the campaign has identified a central question for voters: "Do the American people want to elect the world's biggest celebrity or do they want to elect an American hero?"
Since returning from his overseas trip, Mr. Obama has faced a hail of attacks from Mr. McCain. They began with a charge that the Democrat snubbed wounded American troops by canceling a visit to Landstuhl Regional Medical Center, the large U.S. military hospital in Germany.
The McCain campaign then began airing the ad that associates Mr. Obama with the celebrity culture.
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.
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