Which Newt Gingrich will show up for the final Florida GOP debate?

Here’s the only question that might really matter at Thursday night’s GOP presidential debate in Jacksonville, Fla.: Good Newt or Bad Newt?

Which Gingrich is going to show up? And which, actually, is which?

Is Good Newt the one who, like at Monday’s debate in Tampa, tried to act more statesmanlike, refraining from savagely browbeating both Mitt Romney and the media (except for a brief spat with his rival over Gingrich’s consulting work for Freddie Mac) in a bid to show independents and moderates that he can be presidential when he wants to be?

Is Bad Newt the one who at the debate in South Carolina last week rained his outrage upon moderator John King for asking about the breakup of his second marriage, bashed Romney over his tax returns and tossed red meat to the audience like a crocodile trainer at dinnertime?

Or maybe the Good Newt is the debater his supporters probably want to see tonight, the guy who at a campaign event Thursday had such a full head of steam that he ran off a laundry list of complaints about Romney in almost a single breath, even throwing a Freddie Mac counterattack in for good measure.

“We have to ultimately focus on beating Barack Obama, but we’re not going to beat Barack Obama with some guy who has Swiss bank accounts, Cayman Island accounts, owns shares of Goldman Sachs while it forecloses on Florida and is himself a stockholder in Freddie Mae and Freddie Mac while he tries to think the rest of us are too stupid to put the dots together to understand what this is all about,” Gingrich said.

In South Carolina, Gingrich used a pair of debates to propel him to a surprise victory over Romney. But on Monday in Tampa, Gingrich spent much of the debate on the defensive as Romney went to work over Gingrich’s Freddie Mac work and seemed to spare the rod more than he had in the past.

Gingrich needs a strong showing in Jacksonville to preserve the momentum his South Carolina win provided, but Romney’s campaign and a “super PAC” supporting him, as in Iowa, have battered Gingrich’s name, suggesting that he is, well, maybe a little crazy.

“Unhinged!” read one Romney email blast Thursday, calling the candidate “Dr. Newt and Mr. Hyde.” The Romney campaign likes to throw around words such as “erratic” and “unreliable” to describe Gingrich, but it remains to be seen whether Romney himself will go there Thursday. In that sense, a Gingrich eruption, if it’s too spectacular, could play right into Romney’s hands.

What really has gotten Gingrich riled is that the Romney campaign has begun to suggest that Gingrich, back in the 1980s, was something less than 100 % supportive of President Reagan. Since Gingrich tries to mention his association with Reagan with metronomic consistency, he was predictably outraged.

“To have his campaign take on a lifetime of work and lie about it, frankly, I do find it infuriating. I think it is one of the most dishonest things I’ve seen in politics,” he told reporters after a rally in Mount Dora, Fla. .

If Gingrich is still angry as he sounded then, CNN’s debate could make for must-watch viewing. It begins at 5 p.m. PST.

Times staff writer Seema Mehta contributed to this report.