CEDAR RAPIDS, Iowa — A Republican presidential candidate, Michael Huckabee, insisted he wasn’t trying to pull a fast one when he played a negative TV commercial for the media even as he promised not to air it for voters.

“It was not trying to be tricky; it was trying to be as honest as I could,” the former Arkansas governor said yesterday. “If I’d have really wanted to be tricky, I would have let the ad run three days and then say, ‘No, I’ve had a change of mind.”

Mr. Huckabee had called a news conference Monday to say he was going negative in Iowa, where he is in a tight race with Mitt Romney, and to play the ad that was going to hit the airwaves.

Instead, he said he had a last-minute change of heart and would not air it. Yet he played the ad anyway, prompting incredulous laughter from the media.

Reporters peppered him with questions about it yesterday.

“You know, at the time, I thought it was an important way to prove that we actually had it,” he said of the ad. “Probably if I had it to do over again, I wouldn’t have shown it. And you would have said ‘Aww, show it, you don’t really have one,’ and then you would’ve beaten me up for not showing it.

“Either way I did it, somebody would have had some interpretation of whether it was right to show it,” Mr. Huckabee said. “The one thing I don’t have any regret about, I have no regret at all about pulling the ad.

“I know we did the right thing, and I have no regrets about trying to say ‘Let’s change the tone.’ That was the right decision.”

At that, supporters standing behind the crush of journalists applauded. Mr. Huckabee jokingly pretended it was the media clapping.

“Thank you, press, for clapping for me,” he said. “You laughed at me yesterday; you clap for me today, yes.”

Would it have made Mr. Huckabee look mean to have shown the media the ad anyway? “No, because I don’t think many people will ever see it. I’m not sure that anybody will.”

Told the ad was posted on a blog by Carl Cameron of Fox News, Mr. Huckabee asked, “Oh, is it? How did he get it?”

Iowa’s caucuses, the first votes of the 2008 presidential nominating season, are tomorrow. Polls showed Mr. Huckabee surging ahead of Mr. Romney last month, but Mr. Romney has narrowed the gap with negative ads about Mr. Huckabee’s record of being more forgiving toward illegal immigrants, granting clemency to criminals, and raising taxes. Mr. Huckabee has said the spots may have hurt him.

At the news conference, his campaign had placed signs that read, “Enough is Enough,” a response to Mr. Romney’s ads. The slogan remained on a campaign banner yesterday in Cedar Falls, where Mr. Huckabee played the bass guitar and spoke to about 400 supporters at the Elks Lodge.

“It’s still valid,” Mr. Huckabee told reporters. “I said enough is enough of the negative campaigning. That’s speaking to me as much as anybody else.”