Tonight marks the 19th debate in the Republican presidential contest, the second Florida debate before Tuesday’s primary, and the last debate for nearly a month.

The Republican presidential candidates stand for the national anthem before a debate last week in South Carolina. (Win McNamee/Getty Images)

Tune in to CNN at 8 p.m. Eastern to watch the debate in Jacksonville, and be sure to join The Fix for our usual live chat. (It comes with a money-back guarantee!)

In the meantime, study up for the looming clash with our helpful primer:

* New Newt or Old Newt?: Gingrich just wasn’t himself on Monday night; even his campaign seemed to acknowledge it. And given how much he relies on debates to keep himself viable, that needs to change tonight.

Polling has shown that the bounce Gingrich got from his win in South Carolina on Saturday seemed to have left him by the time Monday’s debate rolled around, and he did nothing at the debate to recover that head of steam.

Can the guy who has already made two comebacks do it again? If he can, it starts tonight.

Keep an eye out for references to Saul Alinsky and attacks on the news media. If Gingrich starts going down that path again, Old Newt is back.

* The return of applause: Part of getting the Old Newt back is up to the audience.

Gingrich and his campaign have said that an applause ban at Monday’s debate hurt their candidate, and they may have a point.

Not anymore.

CNN has said that it will allow applause at tonight’s debate, which should give Gingrich a chance to toss out the kind of red meat that he is known for.

And given that Romney isn’t exactly Mr. Applause Line, that’s good for Gingrich. We’ll see if he takes advantage.

* Does Romney back off Newt?: Perhaps sensing that his prospects are improving in Florida, Romney today appeared to back off his strident criticisms of Gingrich and re-focused himself on an anti-Obama message.

Gingrich, meanwhile, is keeping the crosshairs on Romney.

Romney was the agressor at Monday’s debate, but it’s looking more and more like that role will be played by Gingrich tonight.

If Romney takes the high road, you can rest assured he and his campaign are seeing the same thing the public polls are showing — momentum.

At the same time, by letting up, he may open himself up to another Newt surge. If he continues attacking Gingrich the same way he did at Monday’s debate, it will be an indication that they still see this as a close race and are still concerned that Gingrich could win.

* The long view: As South Carolina showed us, a few days are a long time on the presidential campaign trail.

And given that there are still four full days of campaigning in the Sunshine State after tonight’s debate, it won’t be the last thing on people’s minds as they head to the polls (unlike in South Carolina, where a Thursday debate set the tone for Gingrich’s huge win on Saturday).

In other words, we wouldn’t be counting on anything game-changing unless one of the candidates is feeling desperate or spry.

That said, a debate is a great way to set the tone for the final days of the campaign. Look for the candidates to start broaching new lines of attack in hopes of raising new issues over the weekend.

* Do the disclosures have legs?: Much of the early part of this week was consumed with Gingrich’s Freddie Mac contract and Romney’s tax returns.

But as of now, they are looking more like momentary distractions than game-changing revelations.

Do they come up tonight? Is there anything to be gained by either side pressing for more disclosure? Or is this storyline dead?

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