Huckabee, who has sharply intensified his criticism of the former Massachusetts governor in recent days, tried to reclaim the high road in the midst of a news conference three days before Iowa's presidential caucuses. He told reporters the event had been called to announce the hard-hitting new ad but he had changed his mind about running it on TV.
"We are now committed from now through the rest of the caucuses, that we will run only ads that talk about why I should be president, and not why Mitt Romney should not," he said. "The tipping point was this morning. I just realized that this is not how we run our campaign in this state. We have run it positive. We have gotten here by being positive."
Polls show the race very close between Huckabee and Romney in Iowa. The former Arkansas governor's double-digit lead has evaporated amid a series of Romney ads assailing Huckabee.
Huckabee had long pledged to run a positive campaign and for months had resisted criticizing his rivals directly although he did take unnamed shots at them daily. But as polls narrowed and Romney continued to go after him, Huckabee shifted course over the weekend, calling Romney "desperate and dishonest."
The expectation, fueled by Huckabee himself and his aides, was that he would run ads against Romney in the final days of the campaign. He and his aides hinted a direct response to Romney might be forthcoming, filmed such an ad and called an elaborately staged news conference to announce it.
Then he reversed course.
There was a risk that Huckabee himself would be hurt if he went negative in a TV ad, particularly after spending months branding himself as the upbeat candidate who shunned such politics. Monday's events resulted in him denouncing negativism, though the negative ad got wide coverage.
The 30-second spot accused Romney of "dishonest attacks" on him and on GOP contender- and then criticized Romney on taxes, spending, guns, health care and abortion. "If a man's dishonest to obtain a job, he'll be dishonest on the job. Iowans deserve better," Huckabee said in the ad.
Romney's campaign suggested Huckabee's turnabout - and what it termed his "rather odd press conference" - was a sign of a campaign in free-fall.
Said Romney spokesman Kevin Madden: "To say one thing one minute and then turn around and show an attack ad to reporters the next will, obviously, leave folks with a very cynical view of Mike Huckabee and his message. Mike Huckabee has turned from nice to very hot-tempered now that his record has been examined by voters."
Romney later told CBS News, "The press conference which Gov. Huckabee had today, I think it's confusing to the people of Iowa."
In Des Moines, more than 50 reporters and a dozen cameras were packed into a conference room at a downtown hotel. A backdrop behind a podium on a platform repeated the phrase "Enough is Enough." Placards on either side of Huckabee - five in all - included conflicting quotes from Romney on issues including taxes, abortion, immigration, judicial nominations and guns.
Huckabee arrived and stepped to the podium. His wife, Janet, stood off to the side. A throng of Huckabee's senior aides were nearby.
He denounced the "very negative and nasty tone that the campaign has taken" and said he had mistakenly come to the conclusion that the only thing to do "was to respond with a counter-punch." He said the ad was supposed to start running Monday but just an hour before the news conference, he had ordered his staff to stop it.
"I just feel like we ought to change the tone of the debate, and I'm going to start with me," Huckabee said.
Nevertheless, he showed the ad to the media - after audio problems caused a several-minute delay.
At the press conference, Huckabee told CBS News correspondent Nancy Cordes that he would have faced questions no matter what he did with the ad.
"By the same token, if I came and said we were going to run an ad but we're not going to run an ad, you'd say 'Where's the ad?'" Huckabee said.
Even though the candidate denounced negative advertising at the press conference, he said he would not rule out running such spots in the future, and wanted to see how Iowans responded to his pledge to stay positive.