Debate leaves many GOP candidates scarred

LESTER HOLT, anchor: If the jabs seemed sharper and the tone more contentious during last night's Republican presidential debate , it's likely because there have been some pretty dramatic developments in these final weeks before primary season kicks off. Last night's debate in Des Moines was the first since Newt Gingrich surged out in front of Mitt Romney in Iowa , where the all important caucuses are just three weeks away. And now a new NBC News / Marist Poll shows Gingrich leading in two other key primary battle grounds, news that tonight is changing the tone and the focus of attacks on the campaign trail. NBC 's Mike Viqueira reports.

MIKE VIQUEIRA reporting: The debate quickly got personal.

Governor RICK PERRY: If you cheat on your wife, you'll cheat on your business partners. So I think that issue of fidelity is important.

VIQUEIRA: It was an appeal to conservative voters by Rick Perry and a clear challenge to Newt Gingrich and his history of infidelity. Gingrich was ready.

Mr. NEWT GINGRICH: People have to render judgment. I've said up front openly I've made mistakes at times, I've had to go to god for forgiveness, I've had to seek reconciliation.

VIQUEIRA: Leading in Iowa polls, Gingrich was a frequent target, hitting back when Mitt Romney called him a career politician.

Mr. GINGRICH: The only reason you didn't become a career politician is you lost to Teddy Kennedy in 1994 .

Mr. MITT ROMNEY: That's probably true. If I would have been able to get in the NFL , like I'd hoped when I was a kid , why I'd have been a football star all my life, too. But I...

VIQUEIRA: The brash Gingrich style is playing well with Republican voters. A new NBC / Marist Poll shows Gingrich opening up big leads in key Republican battlegrounds. In South Carolina , he now leads second place Mitt Romney by nearly 20 points. And in Florida , Gingrich is well ahead after a 38-point increase since October.

VIQUEIRA: The debate was at times a free for all.

Gov. PERRY: I'm just saying, you were for individual mandates, my friend.

VIQUEIRA: When Romney challenged, on his support for an individual mandate in health care, suddenly proposed a big wager on the facts to a startled Perry .

Mr. ROMNEY: Ten thousand bucks? Ten thousand dollar bet?

Gov. PERRY: I'm not in the betting business.

VIQUEIRA: Today, critics pounced, noting that $10,000 is one fifth the yearly median income in Iowa .

Gov. PERRY: I'm kind of like, holy mackerel, that's just a lot of money for most people, and I guess not for Mitt .

VIQUEIRA: Other rivals fought for attention. Michele Bachmann said she was more conservative than both front-runners put together.

Representative MICHELE BACHMANN: If you look at Newt / Romney , they were for cap and trade. If you look at Newt / Romney , they were for the illegal immigration problem.

VIQUEIRA: Ron Paul hit Gingrich on his lucrative deal with mortgage giant Freddie Mac .

Mr. RON PAUL: So, in a way, Newt , I think you probably got some of our taxpayers' money.

VIQUEIRA: And Gingrich doubled down on his claim that Palestinians are a, quote, "invented people."

Mr. GINGRICH: Somebody ought to have the courage to tell the truth . These people are terrorists, they teach terrorism in their schools.

VIQUEIRA: Romney called that the wrong approach to a sensitive issue.

Mr. ROMNEY: I will exercise sobriety, care, stability. I'm not a bomb thrower, rhetorically or literally.

VIQUEIRA: And, Lester , late today in New Hampshire , Mitt Romney tried to make light of that proposed wager to Rick Perry . He said after the debate his wife Ann came up to him and said, 'Honey, you did very well, but betting is one