Previewing the Debate in Jacksonville Jason Henry for The New York TimesCrew members prepare for the CNN debate at the University of North Florida in Jacksonville, Fla., on Thursday. This one could be the nastiest, most personal debate yet. Newt Gingrich and Mitt Romney are each signaling a willingness to go nuclear on the other in Thursday night's Republican presidential debate in Jacksonville, a crucial face-off just five days before the primary in Florida. Look at the words that are coming from their campaigns in the hours before the event: From Mr. Romney's campaign: Mr. Gingrich is "unhinged." He's a "historian who re-writes history." He is unpredictable, a "Dr. Newt and Mr. Hyde" character. He's a failed speaker whose ideas were "off the wall." And from Mr. Gingrich's campaign: Mr. Romney has stocks in a bank that "forecloses on Floridians." He is a "guy who has Swiss bank accounts, Cayman Island accounts." He is slinging a "sea of mud." There will be two other candidates on the stage on Thursday - Ron Paul and Rick Santorum. But with polls showing both men trailing badly in Florida, the focus of the night is sure to be squarely on Mr. Romney and Mr. Gingrich. The two-hour, nationally televised debate will begin at 8 p.m. Eastern and will be broadcast on CNN. It is co-sponsored by the Florida Republican Party. Here are a few things to watch for as the debate unfolds: The biggest change from Monday's debate will be the return of the raucous, uninhibited audience. CNN will not attempt to restrain applause from the crowd, which will once again be filled with eager Republican activists. All of that should benefit Mr. Gingrich, whose best moments in South Carolina came when he got the crowd on his side and then fed off their energy. Monday's quiet audience robbed him of the imagery, and of the psychological boost he gets from applause. Mr. Romney's campaign is not happy about the return of the audience; aides say they fear the debates have devolved into reality shows, complete with jeering crowds. But look for Mr. Romney to try to deprive Mr. Gingrich of an audience moment by staying on the offensive. Both Mr. Romney and Mr. Gingrich traveled to Miami this week to woo the region's large Hispanic population. The votes from that community could be crucial to winning the primary on Tuesday. Mr. Romney is likely to raise the issue of a negative radio ad that Mr. Gingrich was forced to withdraw after a torrent of criticism from Hispanic leaders in the state. The ad charged that Mr. Romney was "anti-immigrant," a sentiment that the Hispanic leaders said crossed the line of decency. Both Mr. Gingrich and Mr. Romney are going to have to be careful: How critical can they be without alienating voters? As noted above, the candidates and their campaigns have seemed completely unrestrained during the last 24 hours. Almost no attack has gone unsaid. But there is a big difference between slinging mud at a small rally and doing it on national television. Mr. Gingrich has demonstrated his willingness to show his anger during debates, especially when it is directed at liberals and the news media. And Mr. Romney has had flashes of pique in past debates as well. Both will probably do the same again. But there's a fine line between admirable indignation and petty rantings, and both men will have to try to walk it. It has been weeks now since Mr. Romney's rivals first sought to make an issue of his wealth, and questions about it are likely to come up again. Having released only two years of his taxes, Mr. Romney has generated new questions - about a Swiss bank account that contained about $3 million; and investments in funds that had connections to the Cayman Islands. Both are sure to be the subject of questions for Mr. Romney. Mr. Gingrich has also signaled that he is not ready to abandon the broader questions about Mr. Romney's role at Bain Capital, a private equity firm. Look for whether Mr. Romney has found a way to be more comfortable talking about the subject. Prediction: Mr. Romney will accuse Mr. Gingrich of doing the bidding of liberals. If Mr. Romney has his way, the entire night would be focused on Mr. Gingrich's integrity. In Monday's debate, Mr. Romney repeatedly tried to raise the issue of the ethics investigation into Mr. Gingrich's actions while he was House speaker. Look for that to continue. But Mr. Romney this week opened a new front of attack against Mr. Gingrich's character, alleging that his time as an "influence peddler" deserves further investigation. Mr. Romney even charged that there might be "wrongful activity" in some of Mr. Gingrich's consulting work, though he provided no proof. That could be the most explosive moment of the debate, as Mr. Gingrich tries to defend his record - and his character - against Mr. Romney's attacks. How well he does could determine the arc of the next several days before the primary.