The gloves came off at a Republican presidential debate  as the narrowing field of White House hopefuls tried to undermine frontrunner Newt Gingrich, who did not hesitate to jab back. Gingrich's main rival Mitt Romney quickly sought to sketch out the differences between the two, painting the former House speaker as a Washington insider who does not know what it takes to fix the sputtering US economy. "The real difference, I believe, is our backgrounds," Romney said, touting his own private sector experience and attacking the former Georgia congressman on his position on child labor laws. Gingrich shot back at the former Massachusetts governor: "Let's be candid. The only reason you didn't become a career politician is you lost to (former senator) Teddy Kennedy in 1994." The debate comes just three weeks before Iowa holds the party's first nominating event on January 3 to pick who will challenge Democratic President Barack Obama in November 2012. The largely rural midwestern state barely figures in the general election, but has become key in the nominating races. Given up as politically dead months ago, Gingrich surged to the front of the pack in recent weeks as early contenders Rick Perry and Herman Cain saw their support collapse amidst big blunders and sex scandals. Polls this week show Gingrich with a significant lead over Romney, who had been seen as the party's best chance of beating Obama in 2012 despite the fact that he was unable to win over the party's conservative base. From his opening statement, Gingrich, a giant of Republican politics in the 1990s, portrayed himself as a politician with a "clear record" of results who could get the job done. Romney in turn outlined his plans for job growth in a country where unemployment has remained stubbornly high, despite sinking to a 32-month low of 8.6 percent in November. But the policy debate quickly took on a sharp tone, with the contenders calmly delivering backhanded blows on a variety of issues, including whether voters should take marital infidelity into account in choosing a president. Gingrich is under fire from members of the party's religious base over his admitted extramarital affairs, with one ad calling him "the walking, talking definition of untrustworthy." Romney and Texas Governor Rick Perry both ran ads this week emphasizing their family values credentials. "I've always been of the opinion if you cheat on your wife, you'll cheat on your business partner. So I think that issue of fidelity is important," Perry said. Gingrich said he thinks infidelity is "a real issue" and admitted that he's "made mistakes at times." "I think people have to measure who I am now and whether I'm a person they can trust. All I can tell you is I am delighted at the way people have been willing to look at who I am, to look at what my record has been," he said. Gingrich currently has the support of 27 to 33 percent of likely Republican voters both nationally and in Iowa, while Romney's support ranged from 16 to 23 percent. Gingrich has also narrowed Romney's robust edge in New Hampshire, which votes on January 10, and is ahead of him in South Carolina and Florida, which vote on January 21 and January 31, respectively.