ONE candidate chose a ballroom at the convention centre. Another booked a hotel meeting room. Mitt Romney, the squeaky clean Mormon from Massachusetts, opted for a radically different setting for his final rally before Thursday’s Republican presidential debate in Florida.

His supporters crammed into a side room at Bogart’s Bar above a luxury cinema in Boca Raton. Several were drinking cocktails, adding to a surprisingly festive atmosphere that has suddenly enveloped the much-mocked Romney campaign.

It was not the only Romney surprise to shake up the Republican race last week. Of three opinion polls published in Florida on Thursday and Friday, Romney was four points ahead in two and only two points behind Senator John McCain in the third.

The polls also confirmed a dramatic slide by Rudy Giuliani, the former mayor of New York, who once led the Florida race by 20 points. In Friday’s poll he was 10 points behind Romney in third place, with Mike Huckabee, the conservative former Baptist preacher from Arkansas, languishing in fourth.

A late surge by the 60-year-old former Massachusetts governor is threatening to confound Republican pundits who expected McCain to cement his shaky frontrunner status in Florida and move on to the 24 primaries of Super Tuesday on February 5 in good shape to seize control of the Republican nomination.

Instead, Romney is threatening to turn the race into a dog-fight that could stretch through the summer to the nominating convention in Minneapolis in September. “If they get to March without a clear candidate,” said Craig Sautter, an expert on presidential conventions, “the winner may be decided by backroom deals in Minneapolis.”

At Bogart’s on Thursday it became clear that despite his reputation for flip-flopping whenever he senses political advantage, Romney is attracting new support from Republicans who are beginning to tilt his way after flirting with other candidates.

“I really liked Guliani as mayor,” said Sandra Vargas, one of many transplanted New Yorkers living in Florida. “But I think Romney now looks presidential in a way that Rudy doesn’t.”

Also in the crowd was Mark Garvin, in an “I’m with Fred” T-shirt. When Fred Thompson, the former senator, dropped out of the race last week, Garvin considered other candidates. “I looked at Giuliani, but his poll numbers are garbage,” he said. “I don’t consider McCain a real Republican, so I guess I’m leaning towards Romney.”

The raucous atmosphere of the cinema bar was in marked contrast to the sombre auditorium in West Palm Beach where McCain was trawling for votes.

This gilded stretch of Florida coastline is home to thousands of wealthy Republicans, yet McCain’s successes so far have been based at least in part on support from moderates and independents in New Hampshire and South Carolina.

In Florida only registered party members may vote and McCain’s efforts to turn his South Carolina momentum into an irresistible bandwagon have proved more difficult than he had hoped. His age – 71 – and his past quarrels with the Republican establishment are both proving awkward handicaps.

With Giuliani floundering after what many regard as his disastrous decision to ignore the early primaries, Florida’s door has been opened for Romney to challenge McCain on what many perceive as the Arizona senator’s weakest turf: his lack of economic experience to tackle the looming recession.

Romney’s campaign to date has not endeared him to his fellow candidates. He was named by The New York Times last week as the most disliked Republican in the race, not only because of his elastic views but also because the former investment banker has been ploughing millions from his personal fortune into TV advertising, while rivals have scrabbled for funds after overspending earlier.

He has also antagonised them with criticisms they regard as unfair. McCain declared of Romney that you should “never get into a wrestling match with a pig. You both get dirty and the pig likes it”. Huckabee’s campaign chairman, Ed Rollins, announced that he wanted to “knock out” Romney’s teeth.

The early fuss over Romney’s Mormon faith has largely fallen away. Although he lost the New Hampshire primary to McCain, he won in Michigan, where he was born, and has picked up two smaller states along the way.

Then there is the not insignificant matter of his improbably wholesome family. To the chagrin of some of his maritally challenged rivals, Romney appears on the campaign trail to have stepped out of a Norman Rockwell painting from the 1950s. He is married to Ann, his high school sweetheart. He has five strapping sons, all tall, handsome and eager to tell America how proud they are of their dad, in contrast to Giuliani’s son, who is still bitter that his mother learnt of her divorce at a press conference. The Romney sons in turn are married to beautiful daughters-in-law, who have collectively presented the governor with 11 adorable grandchildren.

When the Romney family marched triumphantly into Bogart’s last week, it was impossible not to be dazzled. The governor even brought one of his grandchildren to the bar, 20-month-old Parker, who giggled and waved to the crowd on cue.

Among those awed by the spectacle was John Pughe, a Boca Raton entrepreneur, who said he was reminded of a Miss America beauty contest. “The Romneys have the Barbie and Ken factor,” he said, referring to the dolls. “For the Republicans that’s no bad thing.”

Romney’s rivals claim that this surface glamour conceals a weak political brain. As Massachusetts governor Romney was a social liberal who supported abortion and gay marriage; as a presidential candidate he opposes both.

Yet Romney may be benefiting from a shift in political priorities as the Iraqi chaos subsides and fears of recession grow. “It’s essential to have a president who has actually had a job in the real economy,” said Romney. He touts his chief executive experience and his success in rescuing the 2002 Salt Lake City Olympics from a series of scandals.

“The economy is the most important issue for us,” said Annabelle Lee, a painter who drove down from Palm Beach with her insurance adjuster husband to check out Romney in person.

“I’ve seen Giuliani but he was a little rough and Romney’s been a success at everything he’s done,” Lee added. “We’ve ruled out everyone else.”

Despite other polls showing that Romney would be badly beaten by Hillary Clinton or Barack Obama in the final vote in November, a victory in Florida would place him in the driving seat for the Super Tuesday vote.

In one of the few memorable moments of Thursday night’s unexpectedly polite Republican debate, Romney won praise for seeming to relish a run-off with Clinton. “Frankly, I can’t wait,” he said. “I can’t even think of Bill Clinton back in the White House with nothing to do.”

More likely, some Republicans are beginning to fear, is that Romney and McCain will trade blows for weeks to come without either delivering a knock-out. If Giuliani and Huckabee choose to stagger onward with their eyes on a possible vice-presidential deal, the stage may be set for the most riotous Republican convention since 1920, when delegates failed to produce a winner after 10 ballots and Warren Harding was chosen during a poker game by leading senators.

“No one can really tell what might happen at a hung convention,” said Sautter. “McCain might say to Romney, let’s make a deal, you be my vice-president, at my age I’ll only serve one term and you can take over. It all depends who grabs enough delegates to make the best deal.”

See Mitt Romney campaigning in Florida

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