Chief correspondent

Newt Gingrich has vowed to take his fight for the Republican presidential nomination all the way to the party’s national convention in August. That may be nothing more than an empty threat by a frustrated candidate with a history of exaggerated rhetoric. But could Gingrich’s battle against Mitt Romney leave the GOP badly divided heading into the fall campaign?

That question will intensify if Romney wins big in the Florida primary on Tuesday. Most election-eve polls show that the former Massachusetts governor has a healthy lead here, although the volatility of the Republican race this year makes forecasting more precarious than in past contests. But already the lines are being drawn over whether Gingrich, if he loses badly, should begin to throttle back or keep the pressure on Romney.

Former Republican senator Mel Martinez (Fla.) said Monday that he cringes at the prospect of a bitter contest continuing into the summer. “It only benefits President Obama,” he said on NBC’s “Daily Rundown.”

Former Alaska governor Sarah Palin, no friend of the establishment, took the opposite view over the weekend on Fox News. She accused Republican elites of trying to “crucify” Gingrich and said it is far too soon to stop vetting the candidates. “If for no other reason, rage against the machine. Vote for Newt,” she said.

Whatever the outcome Tuesday, the Florida campaign has crystallized the battle between Romney and Gingrich. The backlash against Gingrich since his victory in the South Carolina primary on Jan. 21 has made Romney the clear establishment favorite in a party in which tensions between the GOP elite and its insurgent grass roots are still strong. The endorsement of Gingrich by former presidential candidate Herman Cain, a tea party favorite, underscored the split.

Gingrich is hardly the perfect vehicle to lead a tea party protest against the establishment-backed Romney, given his record as former House speaker and later as a Washington consultant. Nor has he found a message that captures what the tea party represented when it first arose.

Still he has the capacity, if not the resources, to wage a long and personal campaign against his rival. In the past few days, he has escalated his attacks on Romney, labeling the former governor as a liberal rather than a moderate and calling his character and honesty into question.

Romney has responded by matching insult with insult. He has belittled Gingrich as a complainer and doubled down on his attacks over his work for the housing agency Freddie Mac. Romney’s campaign appearances are mild compared with the negative ads running on television here, both from the Romney campaign and the super PAC supporting his candidacy.

Political analysts are looking at past nomination battles for clues as to what might happen if the Romney-Gingrich contest continues unabated for a while.

At this time four years ago, Obama and Hillary Rodham Clinton were waging an increasingly nasty Democratic primary campaign against one another, coming out of a South Carolina primary in which some African American leaders accused former president Bill Clinton of playing the race card against Obama. Although many predicted otherwise, Obama and Clinton eventually reconciled.

Some Republicans have drawn comparisons to the 1964 contest between conservative Barry Goldwater and liberal Nelson Rockefeller, a bitter battle that badly split the GOP, led to a landslide defeat for Goldwater and started the conservative takeover of the Republican Party. That comparison is overdrawn. Romney, although distrusted by many conservatives, evokes little of the hatred on the right that Rockefeller did.

Other analysts see parallels with the 1980 Democratic primary between President Jimmy Carter and Sen. Edward M. Kennedy (Mass.). That campaign was both personal and ideological and carried on to the Democratic National Convention. It took years for the wounds to heal among those involved, although Carter and Kennedy never fully reconciled.

In 1976, Ronald Reagan took his fight against President Gerald Ford to the GOP convention, a battle that contributed to Ford’s defeat by Carter that fall and that made it possible for Reagan to become the Republican nominee four years later.

Republicans are cautiously hopeful that the Romney-Gingrich contest will not devolve into something that bitter and lasting, although the increasingly personal nature of it could make it more difficult for the two men to reunite when the race ends.

Interviews with a series of strategists Monday produced a consensus that, however acrimonious the competition appears now, it is unlikely to result in deep divisions once there is a nominee. Obama, they say, will unite the party more than the Gingrich-Romney battle will divide it.

“Once this contest comes to a de facto close, the usual party-unifying steps will be put into effect,” said Pete Wehner, who was an official in the George W. Bush administration. “Some of those on the losing side will swear that they will go to their grave angry at the winner. But calmer heads will prevail, and by the time of the GOP convention, you’ll see the kind of unity that right now seems almost impossible to envision.”

That might be what happens, eventually. For now, prominent Republicans and leading conservatives are taking sides along clear lines of a divide within the party. Those choices have as much to do with reservations about Romney as a true conservative as they do with love for Gingrich.

Romney has regained his footing in Florida with an aggressive strategy. If he wins Tuesday, the next move will be up to Gingrich. How will he respond? The lineup of contests in February favors Romney. The next debate won’t be held until Feb. 22, a long dry spell for Gingrich, who has thrived on such forums.

As he closed out his campaign here on Monday, Gingrich was struggling to find a way to make himself the rightful heir to the insurgency that powered Republicans to victory in 2010. Instead, he remains fixed on winning a debate over who is the real Reaganite in the race. Until he makes that pivot, the question will remain whether he can convert conservative resistance to Romney into a true battle between the establishment and the tea party movement.