First, a newspaper quoted one of the veterans who criticized Kerry's service as saying he was mistaken. Then the group that sponsored the ad released a statement from the same veteran saying he had been misquoted.
The 60-second spot - scheduled to run in small markets in three swing states - Ohio, West Virginia and Wisconsin - features Vietnam veterans who accuse Kerry of lying about his decorated Vietnam War record and betraying his fellow veterans by later opposing the conflict.
But the Boston Globe ran an article Friday quoting one of the veterans featured in the anti-Kerry ad as recanting his statements.
Lt. Commander George Elliott, Kerry's former commanding officer, told the Globe that he had made a "terrible mistake" when he signed an affidavit that suggested Kerry did not deserve his Silver Star.
"It was a terrible mistake probably for me to sign the affidavit with those words," Elliott said.
However later Friday, Swift Boat Veterans for Truth released a statement saying they had a new affidavit from Elliott in which he said he was misquoted and reaffirmed his claims about Kerry.
"I fully reaffirm my statement in the Swift Boat ... [ad] ... in which I said that John Kerry has not been honest about what happened in Vietnam," the statement read.
The Kerry camp, which has used his service in Vietnam as a major selling point, has called the commercial "an inflammatory outrageous lie," and in a letter to local TV stations asked them to pull it.
Communications director Stephanie Cutter said the American people deserve better.
"I think the American people are tired of these misleading attack ads by the Bush-Cheney campaign. We need to talk about real issues," said Cutter.
Republican Sen. John McCain of Arizona, a war hero himself, denounced the Swift Boat group's ad as "dishonest and dishonorable," and pointed out a similar tactic was used against him four years ago during his contentious primary race against Mr. Bush.
On Thursday, McCain called on the White House to condemn the practice.
The White House distanced itself from the anti-Kerry ad, but declined to condemn it.
"We have not questioned Kerry's service in Vietnam," spokesman Scott McClellan told reporters. He also called for an end to the campaign finance reform loophole that helps fund these attacks ads, a number of which have targeted the president.
"We have called for an immediate cessation of these ads and hope John Kerry will, too," said White House spokesman Scott McClellan.
The Kerry campaign also accused the Swift Boat group of having political ties to the Republican Party.
"Far from being a grassroots organization of veterans, this group is a front for the right-wing Texas Republicans to try and take away one of John Kerry's political strengths — his service to the country in Vietnam," the campaign charged in a 36-page document given to reporters.
And, indeed, a wealthy Texan and prolific Republican donor is helping bankroll the anti-Kerry ad campaign.
Houston homebuilder Bob J. Perry has donated at least $100,000 to Swift Boat Veterans for Truth. Perry's other donations in the 2003-04 cycle include $10,000 to the pro-Republican Club for Growth and at least $19,250 to federal candidates and party committees, including $2,000 to Bush's re-election effort.