AP Republicans threw everything they could at Newt Gingrich in a fiery debate on Saturday night, increasingly desperate to stop his momentum towards the 2012 US presidential nomination in the final weeks before voting starts next month. The former speaker of the US House of Representatives responded with a combination of laughs and a steely determination not to let his critics go unanswered, particularly chief rival Mitt Romney. The spirited two-hour debate was the first since Gingrich shot to the lead in polls in Iowa, prompting a round of challenges to his record as a Washington insider, his well-paid consulting work for the semi-federal mortgage agency Freddie Mac, his marital infidelities and his statement that the Palestinians are an "invented" people. Advertisement: Story continues below "Speaker Gingrich has been in government for a long time ... I spent my life in the private sector, I understand how the economy works," Romney said in an early criticism of the longtime politician. "Let's be candid," Gingrich fired back. "The only reason you didn't become a career politician is because you lost to Teddy Kennedy in 1994." This was a reference to when Romney lost a bid for the US Senate, and Gingrich added: "You'd have been a 17-year career politician by now if you'd won." Romney tried to turn that notion around. "If I would have been able to get into the NFL (National Football League) like I wanted to when I was a kid, I'd have been a football star ... losing to Teddy Kennedy was probably the best thing I could have done for the job I'm seeking," he said. "It put me back in the private sector." That got applause. Representative Michele Bachmann of Minnesota hit Gingrich as a Washington elitist, noting acidly that he's made more than $US100 million since leaving Congress, some of it in consulting fees from the Freddie Mac housing agency that conservatives want to dismantle. "When you're talking about taking over $US100 million, and when your office is on the Rodeo Drive of Washington DC, which is K Street, and you're taking money to influence the outcome of legislation in Washington, that's the epitome of the establishment, that's the epitome of a consummate insider," Bachmann said. Gingrich chafed at the criticism, insisting that he was just making a living. "I was in the private sector," he said. "And when you're in the private sector, and you have a company and you offer advice ... you're allowed to charge money for it. ... It's called free enterprise." Some also challenged Gingrich's statement that the Palestinians are an "invented" people. "That's just stirring up trouble," said Representative Ron Paul of Texas. "That was a mistake," said Romney, adding that he would never make such an inflammatory statement. "I will exercise sobriety," he said, implicitly suggesting that Gingrich acts rashly. "I'm not a bomb-thrower, rhetorically or literally." "These people are terrorists," responded Gingrich, in reference to Palestinians. "Sometimes it's helpful to have a president of the United States who tells the truth." He likened his statement to Ronald Reagan calling the Soviet Union an "evil empire". The candidates also talked about the importance of marriage vows, a clear slap at Gingrich, who is in his third marriage. Every other candidate is married to his or her first spouse. "If you cheat on your wife, you'll cheat on your business partner," said Texas Governor Rick Perry, who said his marriage vow was made not only to his wife but also to God. "Character issues do count," said former US senator Rick Santorum of Pennsylvania. "I would not say it's a disqualifier ... but certainly it's a factor ... trust is everything." Gingrich conceded that "it is a real issue" and that candidates and voters have a right to ask. "In my case," he said, "I've made mistakes at times. I've had to go to God for forgiveness." Bachmann slammed both Gingrich and Romney for supporting government mandates that people buy health insurance, supporting "cap and trade" environmental legislation, the $US700 billion TARP bank bailout, and an extension of the payroll tax cut. She referred to them as "Newt Romney". Gingrich reacted sternly: "Michele, a lot of what you say just isn't true. Period." Romney was more jocular, protesting her tying the two together. "I know Newt Gingrich and Newt Gingrich is a friend of mine, but we are not clones," he said to laughter.