Florida, with track record of picking winners, prepares for primary
US Democratic presidential contender Hillary Clinton addresses supporters in Charleston, South Carolina, on February 25, 2016 (AFP Photo/Nicholas Kamm)

Florida -- rich in delegates, and a snapshot of America at election time -- beckons as another gleaming prize for Republican frontrunner Donald Trump next Tuesday and a likely last stand for home state rival Marco Rubio.

The Florida senator, who has led a mainstream Republican charge against Trump, was bloodied in Tuesday's Republican primaries in Michigan, Mississippi, Idaho and Hawaii, picking up zero delegates.

His billionaire nemesis gleefully romped to victory in three of the nominating contests despite an onslaught of negative ads while Texas Senator Ted Cruz took the fourth vote in Idaho.

All of which has raised questions about Rubio's viability in next Tuesday's winner-take-all primary in Florida, a big state with 99 delegates up for grabs.

This is Rubio's home turf, the state that launched the 44-year-old Cuban-American's meteoric political rise.

But a Quinnipiac University poll released Wednesday showed Trump with a two to one lead over Rubio in Florida, 45 to 22 percent, among likely Republican primary voters.

Trump, looking to clear his path to the Republican nomination, has called on Rubio to bow out of the White House race.

"He has a big a decision to make," the real estate mogul said of Rubio in an interview Wednesday with MSNBC, dropping hints of a possible vice presidential spot on a Trump ticket if he steps down before next Tuesday's vote.

"If he runs and loses I think he will never be able to do anything very big politically in Florida.

"I don't think he would be considered by anybody as a vice president and I don't think he could ever run for governor or whatever he might want to run for in the future. So I think running and losing would be risky," Trump said.

Rubio's departure from the race would leave Trump facing only Texas Senator Ted Cruz and Ohio Governor John Kasich, who faces his own do-or-die moment in his winner-take-all home state next Tuesday.

- Rallies and debates -

Florida is a so-called swing state -- it can go either Republican or Democrat in presidential voting -- and the third most populated in the country.

To understand how important it is, consider this: at the close of last week's Super Tuesday primaries in several states, Trump, Cruz and Rubio were already in Florida when they first spoke publicly about the day's voting.

Now, the candidates are spending time and money here. Rallies are being held all over the state, from the more conservative north down to the south, which tends to lean more Democratic.

They will all meet up in Miami, which hosts a Democratic debate on Wednesday and a Republican one on Thursday.

Florida is also an important battle ground for Democrats, with frontrunner Hillary Clinton still struggling with a persistent challenge from Bernie Sanders.

Sanders, a self-declared Democratic socialist, dealt Clinton a surprise defeat in the northern industrial state of Michigan Tuesday, showing his candidacy still has legs.

But in Florida, Clinton has an enormous 30 point lead over Sanders, 62 to 32 percent, with even bigger margins among women voters and Democrats over age 45, according to the Quinnipiac University poll.

The Democrats use a proportional system to allocate the state's 214 pledged delegates to the party nominating convention in Philadelphia in July.

- Picking a winner -

Florida's demographic makeup -- a quarter of the population is Hispanic, and more than 16 percent is African-American -- could help Clinton.

The Sunshine State boasts a diverse population, with lots of people who have moved here from other parts of the country and large Latino and black communities.

The state's voting pattern tends to reflect that of the country as a whole. Since 1964, except for one time, Florida has voted for the primary candidate that ended up winning the presidential election.

Six weeks into the nomination race, the firm favorite both nationally and in Florida is Trump, the outspoken New York billionaire.

Rubio has chalked up only two wins, in Minnesota and Puerto Rico.

Second place is held by Cruz, the ultraconservative who depicts himself as the only man who can beat Trump, spurned by the Republican Party mainstream because of his wild campaign antics, inflammatory comments and polarizing positions on immigration and Islam, among other issues.

"It is going to be tough, because a lot of older voters think Rubio is young, maybe too young. He has a future still ahead of him, and then of course you have the Hispanic community and the natural friction between Cubans and others," said Susan MacManus of the University of South Florida in Tampa.

One question still pending is whether Jeb Bush, the former Florida governor who dropped out of the Republican race in February, will endorse anyone, said MacManus.

His support could be a big help to Rubio, once Bush's political underling, although the two have drifted apart after several nasty exchanges on the campaign trail.