Des Moines, Iowa (CNN) -- From questions over his conservative credentials to his controversial comments over Palestinians to his acknowledged infidelity, Republican White House frontrunner Newt Gingrich was in the line of fire at a GOP presidential debate Saturday night.
And with just over three weeks to go until the Iowa caucuses, the first contest in the Republican presidential primary and caucus calendar, the showdown was more combustible than the three previous showdowns between the GOP candidates.
It didn't take long for the former House speaker and Mitt Romney to trade barbs at the debate, which was hosted by ABC News, the Des Moines Register and the Republican Party of Iowa and was held on the campus of Drake University.
Asked if he agrees with Gingrich's contention that he's more conservative than Romney, the former Massachusetts governor was quick to employ his well-used line that "Speaker Gingrich has been in government a long time," adding, "I spent my life in the private sector."
The former Massachusetts governor, who lost his front-runner status in polling to Gingrich, also highlighted where he and the former House speaker differ on the issues.
"We could start with this idea to have a lunar colony that would mine minerals from the moon," said Romney, referring to a Gingrich proposal to mine for precious minerals on the moon.
Romney also pointed out that he disagreed with Gingrich over altering child labor laws and lowering the capital gains tax for most Americans.
Gingrich calmly responded to Romney, saying, "let's be candid, the only reason you didn't become a career politician is you lost to Teddy Kennedy in 1994. It's a bit much. You'd have been a 17-year career politician by now if you'd won."
Rep. Ron Paul of Texas, who also has criticized Gingrich over the past few weeks, said that the former House speaker has "taken some positions that are not conservative." Paul, who's making his third bid for the White House, and Gingrich sparred over Gingrich's well-rewarded advice he gave to troubled mortgage lender Freddie Mac.
Rep. Michele Bachmann of Minnesota lumped both Gingrich and Romney together, saying, "if you look at Newt-Romney, they were for Obamacare principles. If you look at Newt-Romney, they were for cap and trade."
A lot has changed for the former House speaker since the last GOP debate, a CNN showdown in Washington just before Thanksgiving.
Since then, Gingrich's numbers have soared. He's the front-runner in latest national polling and in new CNN/Time ORC International surveys in Iowa, South Carolina and Florida -- three of first four states that kick off the presidential primary and caucus calendar. The CNN poll also indicates that he's closing the gap with Romney in New Hampshire, which holds the second contest.
Gingrich's campaign was left for dead by many in May and June, after a number of controversies spurred some of his top advisers and staffers to quit, leaving the campaign coffers in the red.
But the former House speaker has performed well in the 11 major GOP presidential debates this year, often acting as the elder statesman while many of his rivals for the nomination attacked each other. He also won over the audiences by repeatedly criticizing the moderators' questions.
Thanks to his debate performances and the fading poll numbers of contenders such as Texas Gov. Rick Perry, Bachmann and businessman Herman Cain, who suspended his campaign last weekend, Gingrich's numbers have skyrocketed.
The debate gave Gingrich an opportunity to defend his controversial comments that Palestinians are an "invented people."
"The fact is the Palestinian claim to a right of return is based on a historically false story," said Gingrich, adding that "this is a propaganda war in which our side refuses to engage and we refuse to tell the truth while the other side lies, and you're not going to win in the long run if you're afraid to stand firm and stand for the truth."
Romney attacked Gingrich's fiery words, saying, "we stand with the Israeli people, we stand with our friends and make it very clear. We're going to tell the truth but we're not going to throw incendiary words into a place which is a boiling pot when our friends, the Israelis, would probably say, what in the world are you doing?"
Gingrich got the last word, responding to Romney by saying, "I think sometimes it is helpful to have a president of the United States with the courage to tell the truth."
Gingrich's three marriages and admittance of an affair were also in the spotlight.
Texas Gov. Rick Perry warned that a politician who cheats on his wife might also cheat in other ways, adding, "if you cheat on your wife, you'll cheat on your business partner, so I think that issue of fidelity is important."
Gingrich appeared almost to be glaring as Perry spoke.
Former Sen. Rick Santorum of Pennsylvania agreed that marital character is important, but added, "I would not say it's a disqualifier"
Gingirch spoke last, admitting again that "I've made mistakes at times. I've had to go to God for forgiveness. I think people have to measure who I am now, and whether I'm a person they can trust."
While Gingrich was the main story of the debate, Romney may have made headlines for offering a $10,000 bet to Perry over their long-running argument over what Romney wrote about healthcare reform in his book "No Apologies."
"Rick, I'll tell you what: 10,000 bucks," said Romney, a multi-millionaire, in trying to make his case that he had not supported implementing an individual healthcare mandate, which is despised by many conservatives.
"I'm not in the betting business, but I'll show you the book," responded Perry.
The bet could give Romney's rivals for the nomination, as well as Democrats, a new attack line to portray the former Massachusetts governor as out of touch with average Americans.
The timing of the showdown between the candidates was crucial. The debate, which will be followed by a second Iowa showdown five days later, comes with just 24 days to go until Iowa's January 3 caucuses.
CNN's Rachel Streitfeld, Shawna Shepherd and Adam Aigner-Treworgy contributed to this report.