Republican presidential candidate Newt Gingrich says he doesn’t regret vowing to run a positive campaign, but Gingrich says he sometimes chafes from that constraint.

Gingrich is the target of attack ads from rivals Ron Paul, Mitt Romney and Rick Perry. The ads accuse Gingrich of “serial hypocrisy” and of benefitting financially from his insider status in Washington, D.C.

“There’s a point where the sheer weight of evidence beats the 30-second attack ad,” Gingrich said this morning. “I’m relying on the good judgement of Iowans to weigh the real history versus the 30-second attack ad.”

Gingrich snapped at rival Mitt Romney earlier in the week, though, accusing Romney of “bankrupting companies” during Romney’s career at a private equity firm. This morning, during taping of “Iowa Press” which airs on Iowa Public Television, Gingrich said it was a remark he’d like to take back.

“I do regret taking a shot at Mitt. It was foolish on my part. He had taken one more shot at me that he knew wasn’t true and made an assertion that he knew was absurd, but it violated all the core principles I have in terms of trying to stay positive despite temptation,” Gingrich said. “It also communicated something I don’t believe in. I think people who run those companies have an obligation to run the companies effectively and to do the best they can and I’ve said in the past, many times, that he’s a good manager.”

Current and former members of congress who served with Gingrich have suggested his leadership style make him unfit for the presidency. 

“I don’t respond to my former colleagues,” Gingrich said. “I tell the public I was a very strong speaker. I helped drive us to a majority for the first time in 40 years. I helped develop the first reelection as a (Republican House) majority since 1948 and, remember, I’m getting this stuff done with Bill Clinton (in the White House).”

Gingrich spent the early morning taping a half-hour conversation with Des Moines Register columnist Kathie Obradovich, for a show that will air this evening on Iowa Public Television, then Gingrich met with the newspaper’s editorial board before sitting down for another half-hour “Iowa Press” interview.  In that last interview, Gingrich seemed unwilling to accept the mantle of front-runner in Iowa.

“I think it’s a three-way race right now,” Gingrich said. “I don’t think it’s clear to me who’s going to win the caucus.”

Gingrich considers himself in that top tier, along with Ron Paul and Mitt Romney.