Three days before the pivotal Republican presidential primary in Florida last month, Rich Heffley was examining the latest opinion poll numbers when he heard that Senator John McCain had won a public endorsement from the most popular and influential figure in the state - Governor Charlie Crist.

Heffley was stunned. The Republican consultant looked at his numbers again. They clearly showed McCain slumping badly behind a late surge by Mitt Romney, the former Massachusetts governor, who on the Saturday before the Tuesday vote had shot into an 11-point lead.

“It was like, ‘Oh my God, what was Charlie thinking?’ ” Heffley recalled. The governor seemed to be betting his authority and political reputation on a loser.

By Tuesday night, the seemingly ill-judged bet had turned into a political jackpot. Crist’s support turned the tide for McCain, who swept Romney aside and is now on the brink of formally securing the Republican presidential nomination.

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That remarkable turnabout has also created a new Republican star. In an interview at his Tallahassee office last week, Crist, 51, modestly deflected speculation that McCain may reward him by choosing him as his vice-presidential running mate. Yet other Florida Republicans were less reticent.

“Charlie would give Elvis a run for his money,” said Ken Pruitt, the Republican leader in the Florida state Senate. “That’s how popular he is in Florida. If McCain wants to win this state in November, Charlie Crist is a no-brainer [as running mate].”

The unforeseen emergence of a youthful, dynamic, and hugely popular Republican governor - think of a skinnier Arnold Schwarzenegger, without the Austrian accent - has added a tantalising twist to the 2008 White House race.

Whether McCain chooses Crist or not - and much may depend on who wins the Democratic battle - Republicans believe they may have found a candidate with the glamour, charisma and political substance to challenge Barack Obama in 2012 or beyond.

After only a year in office as the successor to Jeb Bush, the president’s brother, Crist has rocketed to unheard of approval ratings despite a slumping state economy. He is admired by 77% of Florida voters, many of whom followed his advice and voted for McCain last month.

It is not hard to see why Crist is being talked about in heroic terms. There is a touch of JFK about his yachtsman’s tan and his prematurely silver hair. He tells a lovely story about his Greek Cypriot grandfather sneaking on a boat to America, where he started his working life as a shoe-shine boy.

While McCain has been pilloried for betraying conservative Republican principles, Crist has flourished as a flexible, pragmatic governor who appeals to both rightwing Christians and moderate independents – both of which groups McCain must carry in November.

It did not hurt Crist’s rightwing credentials when, in a previous job as Florida’s attorney general, he became known as “chain gang Charlie” for allowing convicts to be used as road-workers. Yet he also moved to restore voting rights for prisoners convicted of minor crimes.

Like McCain, he tends to base his political judgments on a gut instinct untainted by ideology. Crist noted last week that he endorsed McCain even though the Arizona senator is opposed to a national catastrophe fund that would ease insurance costs for hurricane-plagued Florida homeowners.

“John McCain is not someone who appeases people’s political views to gain their support,” said Crist. “We disagree about the catastrophe fund, but I endorsed him anyway. I never think it’s wise to judge a man on a single issue.”

McCain now has the luxury of delaying his choice as vice-president until after the Democratic team is announced - the Republican convention follows the Democrats in late summer. Numerous names have surfaced on his likely shortlist, notably Mike Huckabee, the conservative former Arkansas governor who has remained in the nomination race despite warnings that he is hurting party unity in a contest he is certain to lose. Huckabee could encourage reluctant rightwingers to support McCain, as would Mark Sandford, the South Carolina governor who helped McCain to victory in a key southern primary.

Yet many Republicans believe that an overtly conservative running mate may alienate moderate voters play into Obama’s hands. They also believe that a key issue in the autumn campaign may be McCain’s age - he would be, at 72, the oldest first-term president to take office. Voters may be more inclined than usual to scrutinise a McCain running mate’s qualifications to govern.

“It’s very flattering to be mentioned,” said Crist in time-honoured reluctant candidate style. “But my focus is really on Florida. I’ve got a lot on my plate as it is.”

That did not prevent him from appearing at McCain’s side after the Virginia primary last Tuesday, nor is it likely to stop him from increasing his national and international profile over the summer. He is leading a Florida trade mission to London in July and recently chatted to Tony Blair when the former prime minister was visiting Miami.

Crist’s Republican allies in Florida make all the right noises about how sad they would be to lose him to Washington, but how worthy a national leader he would be. “If he goes, he will be the next president of the United States after John McCain,” Pruitt predicted.

Yet if Crist sometimes sounds too good to be true, he is far from a certainty as vice-president. He has somehow failed, over his 25-year political career, to acquire a trophy wife and a couple of photogenic kids. He got married in law school, yet divorced after only seven months. He has repeatedly been obliged to deny he is gay.

“There will never be a single man elected president?” Heffley asked scornfully. “I agree with that. Just like I agree there will never be a black man or a woman elected.”

Like all prospective vice-presiden-tial candidates, Crist would be obliged to submit to an intensive background grilling. Yet there has never been a trace of scandal attached to his name, and his supporters point out that his marital status has never troubled Florida voters, evangelical Christians among them.

McCain’s calculation seem likely to depend on the balance he needs between conservatives and independent voters as well as whether Obama or Hillary Clinton is the Democratic nominee. Most Republicans are still praying Clinton will stage a miraculous comeback. They believe she is so divisive that McCain could beat her with Britney Spears as his running mate.

Obama, because of his race and youth, presents McCain with a trick-ier challenge. “There’s no question that Obama is a very gifted, talented politician and he speaks in a very inspiring way,” said Crist. “So the case that Republicans have to make is: do you want inspirational words, or do you want to be inspired by policies that are good for America?”

Crist confirmed that Republicans will primarily take aim at Obama’s lack of executive experience, but Heffley believes their best chance of slowing Obama may actually come from Clinton: “Now Hillary’s in trouble, I think they are going to pull out the long knives,” he said. “She may go negative and try to make life as miserable for Obama as possible.”

Yet the McCain camp already seems to be gearing up for a genera-tional clash against the glamorous black senator from Illinois. After years of war in Iraq, with the economy now faltering, said Heffley, “people are desperate to feel good about something”.

He added: “Barack Obama makes people feel good. And Charlie Crist makes them feel good too.”

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