Six Republican candidates will gather in Sioux City Iowa for the final debate before the Jan. 3 Iowa Caucuses.

Here are five key questions for us political junkies before it begins:

Republican presidential candidates, former Massachusetts Governor Mitt Romney (L) and former U.S. House Speaker Newt Gingrich (R-GA), both gesture during the Republican Party presidential candidates debate at Drake University in Des Moines, Iowa, December 10, 2011. (JEFF HAYNES/REUTERS)

1. Will Rick tick Romney off again? Mitt Romney’s two biggest debate gaffes came in exchanges with Rick Perry, who seems to have a special knack for sending Romney way off message. (Just sayin,’ my friend).

First it was the “I’m running for office for Pete’s sake” line in an exchange about illegal immigrants. Then it was the $10,000 bet. (Note to Romney: Go with a steak dinner next time.)

Perry hasn’t been a real threat to Romney since his own debate meltdowns, but Romney couldn’t help but engage with his former rival at the last debate. His go-to line of “Nice try” worked well to keep him on message in prior debates. It might be worth it for Romney to dust that off again if it means he stays on message and avoids giving the Democratic National Committee another Twitter hash tag.

2. Will Bachmann have another strong night?

Newt Romney.

Rep. Michele Bachmann (R-Minn.) managed to land one of the best two-fisted rhetorical jabs of the campaign, hitting the frontrunners at the simultaneously with a memorable nickname. By linking the two over their more moderate positions on health care and climate change, Bachmann reminded Iowans that if there is a conservative litmus test, she would be one of the few GOP candidates to pass.

The coupling re-framed the Newt vs. Romney showdown, stressing their rivalry and making it harder for them to claim much difference on issues that are key to conservatives. (Romney actually had to say that he is no Gingrich clone).

Bachmann remains one-to-watch in the Iowa caucuses, though she is polling in the single digits. Another strong night on the debate stage where she can succinctly argue her case as the true conservative and a viable “not Romney” and Bachmann could add some much needed momentum to her largely stalled Iowa efforts.

3. How close will Mitt come to calling Newt nuts? Romney has had a everything-but-the-kitchen-sink approach to his attacks on the former House speaker, labeling him a flip-flopper, an unreliable conservative, a career politician, and very wealthy guy. (The exact same attacks have been lobbed at Romney, which just underscores Romney’s “I know you are but what am I strategy” ripped from Pee Wee Herman’s playbook).

But Romney, in the last debate, only hinted at what has become his sharpest, most personal and perhaps most effective line of attack against Gingrich. Call it the Newt as Nutty Professor strategy.

On Tuesday, Romney labeled Gingrich “zany” and in the last debate he mentioned Gingrich’s vision of harvesting minerals on the moon. Romney, whose campaign is led by an opposition research guy, will likely have a treasure trove of these vintage Gingrich ideas that could bolster his argument that Gingrich is more well-suited to a think tank or college classroom rather than the Oval Office.

4. How much will the religious right matter? Perry has made the most expensive play for evangelicals in Iowa, pouring some of his considerable campaign war chest into ads that tout his faith and anti-gay rights stance.And in the last debate, he went for Gingrich’s jugular, saying that a man who cheats on his wife would also cheat on his business partner.

But Gingrich seemed to get the better end of that argument, admitting that he had made mistakes and that he had sought forgiveness. Meantime, Romney has begun to talk more openly about his faith, particularly his mission work as a young Mormon and counseling other members through troubles. Yet he has been fairly disciplined about steering clear of actually mentioning the word “Mormon”--in an interview with Parade Magazine he said his faith was in the Judeo-Christian tradition.

A Bloomberg Iowa poll from November showed that only a quarter of likely caucus voters will be driven by such issues as abortion and gay marriage, suggesting that those social issues are receding as the economy takes center stage.

5. Will the New Newt or the Old Newt show up? Gingrich’s underlying argument about his candidacy is that there are two Newts--one bad (adultery, Nancy Pelosi’s BFF) and one good (faithful husband and good Catholic dad and grandpa, Contract with America).

It is a classic conversion narrative that fits in squarely with a sort of lost, now found redemption meme.

So far, so good.

But if the past is any judge, the new on-message Newt will have a hard time keeping the old, undisciplined Newt at bay. This will be the second debate where Gingrich will be the nominal frontrunner and the fur will likely fly as his rivals try to coax the Old Newt to show up and drop some indefensible rhetorical bombs.

He came close on the debate stage last Saturday when he basically called Romney a wannabe career politician and questioned whether Bachmann had her facts straight. Gingrich’s silver tongue is laced with TNT, which is one reason people like him. But there is also the risk of an explosion, which could leave the New Newt in a cloud of smoke.

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