Jeff Haynes / Reuters
Massachusetts Governor Mitt Romney (L) speaks as former U.S. House Speaker Newt Gingrich (R-GA) looks on during the Republican Party presidential candidates debate at Drake University in Des Moines, Iowa.
Last updated at 11:32 p.m. ET.
The emerging political rivalry between Newt Gingrich and Mitt Romney simmered during Saturday night's GOP presidential debate, but at no point boiled over during the two-hour gathering.
The former House speaker and the former Massachusetts governor sniped at each other throughout the debate, seeking to draw contrasts with each other at a debate at Drake University just 24 days before Iowans participate in the state's Jan. 3 caucuses.
The other four presidential hopefuls, meanwhile, took turns piling on Gingrich, the newly-minted frontrunner according to polls, and Romney, the candidate who's been consistently toward the top of the field throughout the campaign, but hasn't been able to seal the deal with conservatives.
The Gingrich-Romney spat was most stark during the first half hour of the debate, when Romney and Gingrich went at each other over their own political backgrounds. Romney stressed his private sector experience versus GIngrich's time in Congress.
"Let's be candid: the only reason you didn't become a career politician is because you lost to Teddy Kennedy in 1994," Gingrich said in response, delivering a zinger in Romney's direction. "It's a bit much; you'd have been a 17-year career politician if you'd won."
Romney also lampooned some of Gingrich's more unconventional policy proposals.
"Speaker Gingrich and I have a lot of areas where we disagree," Romney said. "We can start with his idea to have a lunar colony that would mine minerals from the moon."
The two candidates sparred lightly throughout the rest of the debate, all while weathering criticism from the rest of the field.
Minnesota Rep. Michele Bachmann linked Gingrich and Romney together on the issue of a health insurance mandate, coining a new moniker to tie Romney and Gingrich together. She said the answer for GOP voters "is Michele Bachmann, not 'Newt Romney.'"
Romney faced criticism, too, from Perry — his main opponent in past debates this fall — over the health reform plan he installed as governor. Perry renewed criticism based on a line in an edition of a book written by Romney, prompting the former Massachusetts governor to offer a $10,000 bet with Perry. It was an eyebrow-raising moment, given the optics of a multimillionaire offering to make a hefty bet, considering the Romney campaign's intent focus on the economy and the middle class.
The Democratic National Committee (DNC), which has been dogged in its criticism of Romney during the primary, picked up on the moment, emailing reporters a list of items the average American family could buy with $10,000.
"Mitt Romney is going to rue the day he offered a $10,000 bet in this debate," said a senior Democratic Party strategist. "Talk about a window in to his out-of-touch soul. And he did it in the same debate where he again called the payroll tax cut for the middle class a temporary band-aid."
The debate had been expected to feature sparring between Gingrich and Romney, each of whom are jockeying for the top spot in the polls. Romney's campaign previewed tonight's showdown by unleashing a wave of criticism of Gingrich the second half of this week.
But the other candidates also sought to use the debate as an opportunity to make a move in the polls, with precious days separating tonight's debate and the beginning of the voting process.
That meant more criticism of Gingrich, who's leapfrogged the pack and to the lead in a variety of state and national polls released this week.
Texas Gov. Rick Perry, for instance, made a thinly-veiled reference to Gingrich's three marriages and past infidelity. Perry said that the candidates' personal lives should be an element for consideration by primary voters.
"if you cheat on your wife, you'll cheat on your business partner," said Perry, who's been making a play of late for social conservative voters in Iowa. "I think that issue of fidelity is important."
And the moderators added new scrutiny of Gingrich, too. The former Speaker found himself under newfound scrutiny at this debate associated with his ascendancy in the polls. He was pressed, for instance, by moderators about his statement this week calling Palestinians an "invented" people.
Gingrich stood by that characterization, and even went further in his characterization of some Palestinian groups: "These people are terrorists."
But the emerging Romney-Gingrich feud was the most closely-watched plot line of the debate, the 12th among Republicans during this primary cycle. While their exchanges weren't always the most fiery, another debate in Iowa scheduled for Thursday could further the divide between the two of them.
Romney perhaps best summed up his criticism of Gingrich in a later exchange between the two over Israel: "I'm not a bomb-thrower, rhetorically or literally."
The debate setting has been where Gingrich, whose debt-saddled campaign was left for dead this summer after suffering a mass resignation by senior staff, has thrived. His resurgence has been driven by strong debate showings.
These gatherings have been of unusual influence in the primary, in part due to the fluidity in the polls. A majority of Republicans in key primary states said in a poll this week that they still may change their mind.
The debate was broadcast on ABC and co-sponsored by the Des Moines Register.
Newt Gingrich leads the polls, but he's facing direct attacks from Mitt Romney's allies about a life marred by ethical and personal controversy. NBC's Mike Viqueira reports.