Leading Republicans on Sunday faulted both presidential campaigns for the increasingly negative tone of their advertising, suggesting the bitter attacks undermine John McCain and Barack Obama's credibility with voters and could backfire.

"Both campaigns are making a mistake, and that is they are taking whatever their attacks are and going one step too far," said former White House political adviser Karl Rove. "They don't need to attack each other in this way."

"There ought to be an adult who says, 'Do we really need to go that far in this ad? Don't we make our point and won't we get broader acceptance and deny the opposition an opportunity to attack us if we don't include that one little last tweak in the ad?'"

In the last week, the McCain campaign has put out an Internet ad accusing Obama of calling Republican vice presidential nominee Sarah Palin a pig when he used the phrase putting "lipstick on a pig" to criticize the GOP ticket as trying to make a bad situation look better. McCain supporters said Obama was slyly alluding to Palin's description of herself as a pit bull in lipstick, but there was nothing in his remarks to support the claim.

The McCain campaign also produced an ad saying Obama favored "comprehensive sex education" for kindergartners; as an Illinois state senator, Obama voted for legislation that would teach age-appropriate sex education to kindergartners, including information on rejecting advances by sexual predators.

In turn, a recent Obama TV ad makes a none-too-subtle dig at McCain's age in saying McCain hasn't changed in the last 26 years. It shows McCain at a hearing in the early 1980s, wearing giant glasses and an out-of-style suit. "He admits he still doesn't know how to use a computer, can't send an e-mail, still doesn't understand the economy, and favors $200 billion in new tax cuts for corporations, but almost nothing for the middle class," the commercial says.

Former New York mayor Rudy Giuliani, who unsuccessfully sought the GOP presidential nomination, said McCain and Obama need to engage more openly in town hall meetings rather than back-and-forth negative advertising.

"I agree that the campaign has gotten too negative on both sides," Giuliani said. "If the two of them are out there answering questions, a lot of these ads are going to get done that way, they're going to be able to confront each other with these things. Senator Obama can explain his views on sex education and just what he was doing with that. Senator McCain can either back off it or agree with it."

Rove said he believed that Obama's "lipstick on a pig" comment was a "deliberate slap at Governor Palin," saying it came too soon after the Alaska governor's pitbull comment not to be. Rove also said while it might be fair to criticize McCain for being a longtime Washington insider, faulting McCain for not using a computer when he can't type due to war injuries is not.

"McCain has gone in some of his ads -- similarly gone one step too far, and sort of attributing to Obama things that are, you know, beyond the 100-percent-truth test," Rove said, without elaborating.