WASHINGTON – John McCain accused Barack Obama of playing politics with race on Thursday, raising the explosive issue after the first black candidate with a serious chance of winning the White House claimed Republicans will try to scare voters by saying he “doesn’t look like all those other presidents on the dollar bills.”

Until now, the subject of race has been almost taboo in the campaign, at least in public, with both sides fearing its destructive force.

“I’m disappointed that Senator Obama would say the things he’s saying,” McCain told reporters in Racine, Wis. The Arizona senator said he agreed with campaign manager Rick Davis’ statement earlier that “Barack Obama has played the race card, and he played it from the bottom of the deck. It’s divisive, negative, shameful and wrong.” The aide was suggesting McCain had been wrongfully accused.

In turn, Obama campaign manager David Plouffe said, “We weren’t suggesting in any way he’s using race as an issue” but that McCain “is using the same, old low-road politics that voters are very unhappy about to distract voters from the real issues in this campaign.”

A day earlier and in response to a hard-hitting McCain commercial, Obama argued that President Bush and McCain have little to offer voters so Republicans will resort to a strategy of fear to keep the White House.

“What they’re going to try to do is make you scared of me,” Obama said. “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 the dollar bills.”

He didn’t explain the comment. But it evoked images of past presidents who grace U.S. paper money, such as George Washington, Abraham Lincoln, Andrew Jackson and Ulysses S. Grant. All were white men, and all but Grant were older than Obama when elected.

Obama long has talked about his physical appearance in speeches, but McCain advisers argue he crossed a significant line by accusing the GOP of scare tactics and alluding to his own race in the same breath.

The back-and-forth was the latest spike in a contest that’s grown increasingly negative despite pledges by both Obama and McCain to run aboveboard campaigns. The daily rhetoric has turned red-hot as both maneuver for advantage and polls show the race competitive three months before the election.

At 46, Obama is serving his first Senate term and working to overcome concerns of voters that he’s not ready to be president. McCain is trying to stoke the notion that the Democrat is too inexperienced to make the judgments necessary to lead a country in times of war and economic straits.

Polls show a close contest nationally and in key battleground states, including electoral prizes like Ohio, Pennsylvania and Florida. The political environment after two Bush terms tilts heavily in the Democrats’ favor, but voter skepticism about Obama has helped keep the contest within McCain’s reach.

In recent days, McCain has been going after Obama with new fervor, painting him as not ready to lead and too liberal for the country. It’s an aggressive approach reminiscent of GOP operative Karl Rove, who orchestrated Bush’s back-to-back victories in part by tearing down Democratic opponents.

Now, several of Rove’s former rank-and-file are in elevated roles in McCain’s campaign, and it shows.

Opening a new front Wednesday, the GOP campaign rolled out a hard-hitting commercial that uses pictures of 20-something stars Britney Spears and Paris Hilton to suggest that Obama is little more than a media darling who is unqualified to be president.

“He’s the biggest celebrity in the world, but is he ready to lead?” the ad asks.

Obama’s campaign countered with its own ad that called McCain’s charges “baloney” and “baseless.”

In Cedar Rapids, Iowa, on Thursday, Obama steered clear of race as he chided McCain, saying: “So far, all we’ve been hearing about is Paris Hilton. I do have to ask my opponent: ‘Is that the best you can do? Is that what this election is really all about? Is that worthy of the American people?'”

At campaign headquarters in Chicago, Obama’s campaign unveiled a new Web site that accuses McCain of “negative attacks and false charges.”

In Wisconsin on Thursday, McCain expressed pride in his “celebrities” ad but also had words of praise for his rival after a questioner at a town hall meeting said Obama “terrifies me.”

“I respect and admire Sen. Obama. We just have stark differences,” McCain replied.

“Campaigns are tough, but I’m proud of the campaign we have run,” he said. “I’m proud of the issues we have tried to address with the American people. … All I can say is we are proud of that commercial.”

Obama campaign manager Plouffe retorted later, in a conference call with reporters, “We can most assuredly tell you that voters around the country do not think there’s anything substantive about this latest ad, do not think it’s something that John McCain should be proud of.”

The Democrat’s campaign has been operating under an edict to leave no attack unanswered lest he be tagged with an unshakable label. In 2004, Democrat John Kerry never recovered from the Bush campaign’s efforts to tag him a flip-flopper and elitist, as well as a Republican-aligned group’s questioning of his war record.

Mindful of how a such a damaging narrative can take hold, Obama’s campaign set up a Web site to dispel persistent Internet-driven rumors about his patriotism and religion, and he has sought to reassure voters on the campaign trail.

Often, he refers to his distinctions as a candidate and says that he’s aware there are doubts among some voters because, for example, he has “a funny name.” Obama, the son of a white mother from Kansas and a black father from Kenya, also has been known to acknowledge his appearance differs from previous candidates but then to add that the differences are not just about race.

“I know that I don’t look like the Americans who’ve previously spoken in this great city,” he said last week in Berlin. And on Tuesday, in Springfield, Mo., he said: “It’s a leap, electing a 46-year-old black guy named Barack Obama.”

Race generally remained in the background during the Democratic primary. The issue burst into the open last spring when Obama’s former pastor, Jeremiah Wright, came under fire for sermons in which he accused the government of conspiring against blacks. Internet videos of his comments threatened great damage to Obama’s campaign.

Seeking to stem the fallout, Obama gave a high profile speech about racial tension in the country and later left Wright’s church.

Associated Press Writers Scott Bauer in Racine, Wis., Mike Glover in Cedar Rapids, Iowa, and Ann Sanner in Washington contributed to this report.