There are many unanswered questions heading into tonight's CNBC GOP presidential debate. Will the circus surrounding Herman Cain's sexual harassment allegations overshadow the debate? Is this the debate Mitt Romney finally pulls away from the rest of the field, or will the GOP frontrunner continue be pounded by the other candidates with the "anyone-but-Mitt" drumming? Can Newt Gingrich break into the first-tier of GOP presidential candidates? And which Rick Perry will show up--the gaffe-prone candidate who's presidential candidacy has faltered in previous debates, or the giddy and drunk-sounding candidate who delivered a speech in New Hampshire that made headlines for all the wrong reasons?

These are just some of the storylines going into the latest Republican debate, which starts at 5 p.m. PT.  Though the debate--the first since the Cain scandal broke--is supposed to focus on economic issues, you can bet the candidates will bring up the sexual harassment allegations against the former CEO of Godfather's Pizza.

Here now are three things to watch for in tonight's debate: 

1) Will Herman Cain's troubles overshadow the debate?

You may recall that in the last debate, Cain, then a target because of his rising poll numbers, was attacked by his fellow presidential candidates for his "9-9-9" plan. But one day after holding a press conference in which he denied allegations of sexually inappropriate behavior and claimed he "never acted inappropriately with anyone," Cain will most likely have to defend himself against the recently surfaced accusations. The question here does not appear to be "if" the candidates will bring up the scandal, but "when" and "who will be the first to do so." The Washington Post also brought up the possibility that one of the moderators might bring up the issue.

So far, the sexual harassment scandal has not appeared to hurt Cain's campaign--at least not in the polls--as many of his supporters do not believe the allegations. Cain's botched attempts to contain the fallout also seem to not have hurt his candidacy. In fact, since the scandal broke on October 30, Cain has raised more than $2 million.

Tonight, however, Cain will have to face-off against his Republican rivals, including frontrunner Mitt Romney who has made the strongest condemnation of any of the candidates against Cain, calling the allegations "particularly disturbing."

2) Speaking of Mitt Romney, is this the debate he finally pulls away from the rest of the field?

Republicans needs to face facts: with less than two months to go to the Iowa caucuses, Mitt Romney is the definitive frontrunner in the race. A new Gallup Poll shows nearly half of all Republicans believe the former Massachusetts governor will win the nomination. Romney has been able to withstand challenges from Rick Perry, who entered the race with much fanfare that seems to fade a little more each time the Texas Governor opens his mouth (especially during the debates), and from Cain, who's stock was quickly rising prior to the scandal breaking.

Yet, as The Daily Beast noted, "the last two weeks have seen the anybody-but-Mitt movement crystallizing like never before." Need evidence? Check out this website devoted to not electing Romney. Even Democrats are getting in on the action: right ahead of the debate tonight, the Democratic National Committee released this video ripping Romney's free-market position.

Romney has thus far fared well in the debates, but as we get closer to the the January 4, expect the attacks to be more frequent and possibly more heated as well.

3) Can Newt Gingrich use this debate to vault himself into the field's top-tier candidates?

Call him the comeback kid. Newt Gingrich's campaign had all been written off after a rough start that included a mass-exodus by his top campaign staffers in the beginning of June. However, the former House Speaker's campaign finally appears to be hitting its stride, as evidenced by his recent rise in some of the polls. In a Gallup Poll conducted between Nov. 2-6, Gingrich polled at 12 percent, right behind Romney and Cain who each garnered 21 percent of Republican support.

One potential (major) issue for Gingrich: his campaign is more than $1.1 million in debt, the most of any of the Republican candidates.

Still, as candidates like Cain and Perry falter, there's a major opening for Gingrich to surge into second behind Romney. Tonight's debate offers Gingrich a chance to prove to voters he's the real deal. His past performances, however, have been a mixed bag. As The Washington Post observed, "debates are often feast or famine when it comes to Gingrich. He can be either really good, or he can wander off-topic talking about arcane legislation like the banking bill 'Sarbanes-Oxley' and never really make a dent."

Ultimately for Gingrich, it all boils down to this: he must have another strong debate showing tonight.

Bonus: Can Rick Perry put together a good debate performance?

The short answer: most likely not. A string of gaffes in speeches and a series of poor debate performances have left Perry, once the frontrunner for the GOP nomination, in the second-tier of candidates. Things were so bad that Perry last month considered not participating in any more debates and focusing all his efforts on the campaign trail. Perry has himself admitted that he is not a good debater, and in a recent ad even goes so far to say that he is a "doer, not a talker."

Expectations of Perry's debate performance are so low that at this point he really has nothing to lose in this debate. One thing's for sure: Perry most likely will not to win the nomination, or votes for that matter, based solely on his debate performances.