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After dancing with a full field of alternatives to Mitt Romney, Republicans, if opinion polls are to be believed, have settled on Newt Gingrich.

The race for the GOP presidential nomination is squarely between these two men a month out from the Iowa Caucus.  And while they share similarly monosyllabic and atypical first names, they represent a sort of yin and yang for Republican voters.

The two will meet on a stage at Drake University in Iowa Dec. 10, when ABC News and Yahoo! sponsor a GOP presidential debate with the Iowa Republican Party and the Des Moines Register.

Send your questions for Gingrich and Romney.

"The biggest difference between us is probably our life experience," Romney told Sean Hannity on the radio recently. "He has spent his last, I don't know, 30, 40 years in Washington and is a career politician."

Romney has tried hard to make his status as a former businessman and one-time governor a selling point of his campaign.

"I only spent four years as governor, but I didn't inhale," is his canned line on the campaign trail.

But many Republicans aren't buying. And the latest alternative to gain in the polls is Gingrich, a man who very certainly did inhale politics, but has been out of the game so long that he can simultaneously argue he'd be coming at official Washington from the outside.

"I'm not a Washington figure despite the years I've been here," he said back in May.

Read Newt Gingrich's story.

Read Mitt Romney's story.

Gingrich has also argued that his experience in government will help him be a better president. And he's dismissive when other Republicans try to paint his past as a liability.

"The fact is we've tried a inexperienced amateur," Gingrich told ABC's Jake Tapper. "He's a disaster. It would be nice to actually have somebody who actually knows what they're doing," said Gingrich. "My answer would be that if you look at my track record, balancing the budget for four years, paying off $405 billion in debt, reforming welfare, two thirds of those people go to work or go to school.

"First tax cut in 16 years, largest capital gains tax cut in history, unemployment down to 4.2 percent.  First national Republican majority in the House in 40 years, first re-elected majority since 1928, person who worked with Ronald Reagan, supported Ronald Reagan, I'm happy to contrast that with anybody else, but I think that's a check off, fine, we got it. Now let's talk about what are you going to do for America, what are you going to do with the American people, and I find audience react very intensely to a positive solution-oriented approach."

But Gingrich's accomplishments in the government are also, in a lot of ways, Bill Clinton's accomplishments. Everything that came to pass under Newt Gingrich as Speaker of the House, also got by President Clinton's veto pen.

Romney was a successful Republican in a blue state. He signed into law health reform that became a model for the national system Democrats enacted in 2010.

All this leaves Republicans with a choice between two men who represent a sort of yin and yang of American politics.

One seems groomed for the White House with a political pedigree, a previous campaign in 2008 and movie star looks. The other was long thought to be done as a politician, who had reached the heights of power and provided the conservative foil to a previous president.

Most obviously different is their appearance. Mitt Romney is spit-shined and well-creased. He's fast-walked and energetic. He's got a dark head of gelled hair with silver at the temples. He's in impeccable shape. Gingrich, on the other hand, is a bit rumpled, with a shock of white hair. He's not trim and admits "I should lose weight," but says he's in very good shape and can go for days on the road with little sleep.

They're one of the best educated duos to face off in a primary. Gingrich was an academic turned politician - a former professor with a PhD in history. Romney went to both law and business schools at Harvard.

Romney is Mormon - a minority religion in the U.S. that is viewed with trepidation by some conservatives, especially in early primary states. He's been married to the same woman his entire adult life. Gingrich has married three times - something that some social conservatives view with trepidation. And he has been on a life-long religious journey. Gingrich was raised Lutheran and later became Southern Baptist before settling n Catholicism with his current wife Callista.

Both men are wealthy, but the circumstances of their wealth speaks to their differences. Gingrich became wealthy and a successful businessman in large part because of his government service, founding a network of companies and think tanks to use his brand - former Speaker of the House and Republican intellectual - to influence policy, advise corporations, and sell books.

Romney, despite a political pedigree from his senator and presidential candidate father, went about things the other way around. He found success in politics only after becoming wildly successful in business at the helm of Bain Capital Management.

Both men have come under fire from conservatives for some of the same moderate views. But they came at those views at distinctly different periods in their careers. Romney was more moderate in trying to get elected as a senator and later as governor of Massachusetts. Gingrich started off as a conservative agitator and won control of the House of Representatives for Republicans by opposing Clinton and pushing a "Contract with America." But he had to compromise with Clinton to end a government shutdown and pass landmark welfare reform legislation. Gingrich became more moderate on some issues  at the heights of his power and, for a time, after leaving office. He appeared in a commercial with then-House Speaker Nancy Pelosi in 2009, arguing that humans contribute to climate change and that something should be done about it. He now says that was a mistake.

Romney's most controversial policy evolution is in the area of abortion - something he said should be safe and legal in the U.S. in 1994 during an unsuccessful run for the U.S. Senate against Sen. Edward Kennedy. Since moving to the national stage, Romney's position on abortion has evolved. He now thinks Roe v. Wade, the landmark Supreme Court decision ensuring a woman's right to choose, should be overturned.

Read about Mitt Romney's policy shifts over his career.

Read about baggage Newt Gingrich brings to his campaign.

Romney has recently started to draw contrasts between himself and Gingrich - saying critically, for instance, that Gingrich had a long career in Washington. Before that, Romney's campaign launched attacks on Rick Perry. But Gingrich, for the moment, has shied away from being critical of his counterparts, even as Romney, and especially Ron Paul, have attacked him for his long history in Washington and his previous policy positions.

Romney's campaign has been long in the making. He ran in 2008 and has a sophisticated ground operation, particularly in New Hampshire. His staff is disciplined and has been with Romney in some cases for years. Gingrich's run felt more spur of the moment when he jumped in the race.  Some staffers quit over the summer when they felt Gingrich was not committed enough to the campaign. He has more than rebounded from those setbacks to become the frontrunner. Through all that time, Gingrich's strategy, as Romney's was over the summer, has been to focus entirely on President Obama. He won't say anything bad about the other Republicans on the stage.

All this leaves Republicans with a choice between Romney's steady campaign, which has been consistent, but never caught hold with more than a quarter of the GOP voters, according to polls. Gingrich was long out of the spotlight as a candidate when his staff quit. His candidacy has been mercurial and while he has jumped to the head of polls, it remains to be seen if interest in him will last.