CBCNews.ca and CBC News Network will have live coverage of today's Republican and Democratic presidential primaries in Florida, Ohio, Illinois and North Carolina, and will provide the latest results once polls start closing at 7 p.m. ET. 

Marco Rubio's face was a mask of cheerful tenacity. His voice — barely aided by a dinky-sounding bullhorn, then a crackly microphone, then back to the bullhorn — was a distant murmur.

As supporters last night in his hometown of West Miami strained to hear him, shushing each other on the eve of today's Florida primary, it felt like a fitting moment for a fading campaign.

Here was Rubio, all hope on the surface, yet so easily drowned out by competing noise.

"We have to vote tomorrow," the junior senator from Florida said. "Make sure no one stays home!"

Unlike previous contests, today's primary is viewed as a do-or-die election for him. It could end the 44-year-old's presidential campaign and seal the blustering front-runner Donald Trump as the GOP nominee.

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A billboard declaring Florida as "Marco Rubio country" is seen outside Rubio’s campaign headquarters in West Miami. (Matt Kwong/CBC)

With his political future on the line, Rubio, standing on the bed of a pickup truck last night, remained upbeat while addressing the crowd at the outdoor basketball court he played on as a youth. He grinned broadly.

"I can't wait to stand on that stage in Cleveland, Ohio, in July, and accept the nomination for Republican candidate," he said at the West Miami Recreation Center.

Rally attendees like Ivis Flores shared his wishful thinking. Flores said she was praying for Rubio, though she conceded this was possibly the last time the candidate might hold a rally for a presidential bid.

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Volunteers work the phones at Rubio’s campaign headquarters in West Miami on Monday morning. (Matt Kwong/CBC)

"We don't lose faith," said Flores, 56. "No matter what, he is our winner."

Lawn signs around West Miami and Little Havana still declare that "Florida is Marco Rubio country," but new polling data cast doubt on his chances.

The latest Monmouth University Poll released Monday puts Trump well ahead of Rubio, with 44 per cent to Rubio's 27 per cent favourability.

The RealClear Politics average in Florida, taking the latest poll into account, has Trump with 42.9 per cent, followed by Rubio with 23.8 per cent — a spread of 19.1 points.

Pundits agree that if Rubio cannot carry his home state and collect all 99 of its delegates, it won't be just a setback that stings; it will deal the final blow to his political run in his own backyard.

And there is no Senate seat to break the first-term senator's fall.

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Julianne Gonzalez, 21, calls likely voters at Rubio’s campaign headquarters on Monday morning. (Matt Kwong/CBC)

Months ago, Rubio was the young Establishment hopeful riding a wave of "Marco-mentum," and buoyed by a surprisingly strong showing in the Iowa caucuses.

That neither Rubio nor former Florida governor Jeb Bush might defeat Trump to win their home state seemed, at one time, unfathomable. Bush left the race after a disappointing South Carolina primary showing.

'People here love Marco'

Now Rubio, whose South Florida supporters and Cuban-American loyalists still refer to him as "Miami's favourite son," confronts the possibility of being flattened by the Trump steamroller.

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Volunteers work the phones for Rubio in West Miami. (Matt Kwong/CBC)

Asked what will happen to Rubio's campaign should he lose Florida, rally attendee Steve Bovo, carrying his five-year-old son on his shoulders, demurred.

"I don't think this is going to be his last night," he said. "I think he's going to win tomorrow. People here love Marco, and we think there's going to be more campaigning ahead."

Mac Stipanovich, a Rubio supporter and long-time Florida Republican strategist, took a more fatalistic view.

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Nyvia Sagre, 62, displays a Marco Rubio sign during a ‘homecoming’ rally for the Republican presidential candidate. Sage says she doesn’t take stock in polls that suggest Donald Trump will win Florida. (Matt Kwong/CBC)

"It's do-or-die for him. Anyone who hasn't been lighting up the scoreboard elsewhere, who fails to carry his own state, should leave the race," Stipanovich said. "That would be true of John Kasich in Ohio, it would have been true of Cruz in Texas, and I think it's true with Marco."

If "Marco-mentum" was alive anywhere, it was at Rubio's Miami campaign headquarters. But at around 10:45 a.m. on the morning before today's primary, the operation was still creaking to life.

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Ivis Flores, right, and her husband Leandro, attend a Marco Rubio rally at the City of West Miami Recreation Centurion Monday night. (Matt Kwong/CBC)

Chairs sat empty and headsets lay untouched at unmanned computer terminals. Six keen phone-bank volunteers asked the same questions in English and Spanish: "Can we count on your vote for Marco?"

Volunteer Julianne Gonzalez, 21, liked the answers she was hearing on the other end of the line.

"Que bueno, que bueno!" she told one pledged Rubio backer.

Yoandry Galan, 24, called about a dozen residents. Everyone who answered the phone in the last 20 minutes, he said, had committed to vote for Rubio in today's election.

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Sara Cortes, 17; Eliett Cortes, 41, and Jorge Cortes, 46, attend Marco Rubio’s ‘homecoming’ rally in West Miami. (Matt Kwong/CBC)

"We really need him to win Florida," he said. "If he doesn't, that's a setback, but I think he's going to win, so there's no need to worry about that."

The swirl of Spanish and English chatter picked up by 11:30 a.m. in a last-gasp push to revive the campaign.

No-show reputation

As far as Rubio's political vulnerabilities elsewhere in the Sunshine State, Robert Watson, who teaches American studies at Florida's Lynn University, noted that some Republicans were embittered by his apparent shirking of responsibilities during his first four years in the Senate.

When the story broke last February that Rubio had the worst voting attendance record in the Senate, his reputation as a congressional no-show became a vulnerable charge for him.

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El Mago, the owner of El Mago Del Fritas, a popular Cuban diner in West Miami, says he will either vote for Rubio or abstain from voting. (Matt Kwong/CBC)

"There was a lot of buyers' remorse from the voters," Watson said. "A lot of Floridians were thinking, 'My god, why did we pick this guy?'"

Even so, it's hard to deny Rubio has deep roots in West Miami, where he grew up as the Cuban-American son of a bartender and a maid.

El Mago, the 77-year-old owner of the no-frills Cuban diner El Mago De Las Fritas, where Rubio grew up eating chopped-chorizo burgers and sipping sweet Cuban coffee, remembers him well.

If Rubio were not on the ballot, El Mago said, he would likely abstain altogether. It's the way most of the Cuban-American patrons feel, he said, speaking in Spanish through an interpreter.

Ivan Marquez, the restaurant's 29-year-old line cook, says the patrons are definitely Republican, definitely proud of its Cuban-American lineage, and definitely not on board with Trump.

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Ivan Marquez, 29, the line cook at El Mago Del Fritas, a popular Cuban diner in West Miami, says Republican presidential candidate Marco Rubio was a frequent patron. (Matt Kwong/CBC)

"They always joke about it. They think he's a joke, that he'll never make it president," Marquez said, adding there would be "some shock" in the community if Rubio does not win in Florida today.

Just because the El Mago crowd skews Republican doesn't mean the person preparing the food is necessarily a Rubio supporter, however.

Asked whether he planned on voting for Miami's favourite son, Marquez laughed, then outed himself as a rare Democrat among the staff. 

"I'm a Bernie Sanders guy," he said.