The return of nasty Newt Gingrich?

DES MOINES, Iowa -- Newt Gingrich always seemed like an unlikely candidate to be the man to keep the Republican presidential primary from becoming a less than cordial affair. Gingrich was known as a short-tempered bomb thrower during his days as House speaker, a man with a penchant for belittling his foes with "childish political insults," in the words of GOP lawmaker-turned-television host Joe Scarborough, who served in the House of Gingrich.

Yet Gingrich has repeatedly called for comity during the GOP primary process, arguing that "Attacking fellow Republicans only helps one person: Barack Obama." He vowed not to run negative ads, instead offering a positive, issue-oriented campaign that would help keep the eventual nominee from being weakened before the general election.

But Gingrich's rivals - and their supporters - weren't listening. A Super PAC backing Mitt Romney spent millions of dollars to run a torrent of negative ads against Gingrich in Iowa, and Ron Paul's campaign also ran spots in the Hawkeye State harshly criticizing the former Speaker. The ads seemed to work, diminishing Gingrich's standing in the polls. They also seemed to anger Gingrich, who called the notion that Romney couldn't stop the ads "baloney."

Cracks in Gingrich's positivity soon began to show. After Romney called on Gingrich to return the $1.6 million-plus he was paid by mortgage finance firm Freddie Mac, Gingrich shot back: "If Governor Romney would like to give back all the money he's earned from bankrupting companies and laying off employees over his years at Bain, then I would be glad to listen to him." The comment might have come from the Obama reelection team, which has used Romney's years at Bain Capitol to portray him as an out-of-touch job destroyer.

On Iowa caucus day yesterday, the damn broke. Appearing on CBS News, Gingrich called Romney a liar operating under the "pretense that he's a conservative."

"Here's a Massachusetts moderate who has tax-paid abortions in 'Romneycare,' puts Planned Parenthood in 'Romneycare,' raises hundreds of millions of dollars of taxes on businesses, appoints liberal judges to appease Democrats, and wants the rest of us to believe somehow he's magically a conservative," said Gingrich.

Then came Gingrich's remarks following his disappointing fourth-place finish in the caucuses, when he said that while he won't be running negative ads, "I do reserve the right to tell the truth."

"And if the truth seems negative, that may be more a comment on [Romney's] record than it is on politics," he added in remarks whose tone suggested personal animosity toward the former Massachusetts governor.

Gingrich's apparent pivot toward a more negative tone toward Romney could spell trouble for the frontrunner, who largely avoided criticism in the fight for Iowa. Gingrich can be an effective critic, particularly during presidential debates, for of which will take place before the Sept. 21 South Carolina primary. If he decides - or has already decided - he wants to keep Romney from the nomination at any cost, he could do some serious damage to his rival.

Of course, that's exactly what Gingrich said Republicans shouldn't be doing for fear of acting as an unwitting ally to President Obama. But Gingrich has been known to let his personal feelings get in the way of his political goals - most famously when he suggested his having experienced a "snub" by President Clinton during an airplane fight, including being asked to "get off the plane by the back ramp," contributed to the 1995 government shutdown - and there's no reason to think he might not do so again.