DES MOINES, Iowa (AP) -- Attacked as a lifelong Washington insider, newly minted Republican front-runner Newt Gingrich parried criticism from Mitt Romney in campaign debate Saturday night, telling the former Massachusetts governor, "The only reason you didn't become a career politician is because you lost to Teddy Kennedy in 1994."
'That's probably true," replied Romney, who lost that Senate contest. He then quipped that if he'd achieved his childhood dream, "I would have been a football star all my life, too."
Gingrich defended himself against attacks from Texas Rep. Ron Paul and Minnesota Rep. Michele Bachmann as well as Romney, the former front-runner, in the first debate since he soared to the lead in polls nationally and in Iowa. The state's caucuses on Jan. 3 will kick off the competition for Republican National Convention delegates who will pick an opponent to President Barack Obama.
All six Republicans on stage assailed Obama's handling of the economy, the overriding issue of the election, yet split down the middle on legislation making its way toward a year-end vote in Congress to extend a Social Security payroll tax cut into 2012.
Romney, Gingrich and Paul said they favored it. Bachmann, Texas Gov., Rick Perry and former Pennsylvania Sen. Rick Santorum said they opposed the measure.
Whatever the impact of their differences on the presidential race, the internal disagreement could well portend difficulties for legislation that Obama has proposed and Republican leaders in Congress view as essential if the party is to avoid being tagged for raising taxes.
The tone of the debate was generally respectful, the stakes ever higher as six rivals met onstage in the Iowa capital city. The debate was the 12th since the long campaign began and the first since Herman Cain's candidacy imploded after allegations of sexual harassment and an extra-marital affair.
Gingrich's personal life has become a campaign issue, too, and it came up briefly Saturday night.
Asked whether marital fidelity was a valid concern for voters choosing a candidate, Perry said, "If you cheat on your wife, you'll cheat on your business partner. It's a characteristic people look at."
Gingrich, who has been divorced twice and has admitted past infidelity, said the issue was an important one, then added, "I've made mistakes at times and I've had to go to God for forgiveness."
For Gingrich, the debate brought new standing -- a center position onstage that comes with being a leader in the polls -- as well as the challenge of fielding criticism from his rivals.
Other contenders sought to stand out.
Bachmann referred to the former speaker and the one-time Massachusetts governor as "Newt-Romney," saying the two men hold similar views on health care, illegal immigration, cap-and-trade legislation and the payroll tax cut extension.
Paul said he, unlike the others, often took lonely conservative stands in Congress. "I end up sometimes, believe it or not, voting all by myself, thinking why aren't there people paying attention?"
Gingrich also defended his recent statement that Palestinians were an "invented" people. Several of his rivals said they generally agreed with his description, but Romney said that with the remark, the former speaker may well have made it more complicated for Israeli Prime Minister Netanyahu to move toward peace with Palestinians.
He said it is important to show sobriety, care and stability, an unspoken accusation against Gingrich, adding, "I'm not a bomb thrower, rhetorically or literally."
Gingrich responded by declaring he was a conservative in the mold of Ronald Reagan, a president who he said spoke the truth, as when he called the Soviet Union the "evil empire."
Gingrich's decision to invoke Kennedy, the late senator from Massachusetts, served as a dual reminder -- that Romney has been running for office since the mid-1990s and also that he lost to the man whose politics conservatives detested above all others.
As for the question of whether he would have become a career politician if he'd beaten Kennedy, Romney tried to turn the tables, saying his defeat in 1994 "was probably the best thing I could have done for preparing me for the job I am seeking, because it put me back in the private sector."
One of Romney's campaign calling cards is his career as a businessman, a time he says helped him understand how jobs are created.
Paul has been airing television commercials in Iowa attacking the former House speaker, and Romney's campaign has become increasingly critical of him, bolstered by a multimillion-dollar television ad campaign that is financed by allies. Under questioning from Paul, Gingrich said he had never lobbied for Freddie Mac, a quasi-government agency that paid him at least $1.6 million to provide strategic advice. Paul shot back, "It's the taxpayers' money, though. We were bailing them out."
By the debate's last moments, the contenders found something nice to say about one another, an obvious attempt to build their own support at the expense of others.