Sen. Marco Rubio Marco Antonio RubioFlorida senators pushing to keep Daylight Savings Time during pandemic Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll Intelligence chief says Congress will get some in-person election security briefings MORE (R) on Tuesday is facing a last stand in his home state of Florida that will mark a turning point in his political career.

Rubio trails GOP presidential front-runner Donald Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE by double digits in recent polls, a stunning development few would have predicted in spring 2015 when the rising star launched his White House bid in Miami. Simply put, if Rubio loses Florida’s primary, he’s finished in 2016, and there will be many questions about his political future.

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When his campaign began, Rubio, 44, was one of the favorites to win the GOP nomination. Democrats saw the Cuban-American as a formidable general election candidate who might give their likely nominee, Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE, fits.

Rubio showed confidence in himself, opting to run against his onetime mentor, former Florida Gov. Jeb Bush (R), and forgoing a run for reelection to the Senate. In many ways, he was all in.

A year later, Rubio has outlasted Bush, but his campaign is now running on fumes.

He has won 163 delegates, according to an Associated Press count, nearly 300 fewer than Trump has and more than 200 behind Ted Cruz Rafael (Ted) Edward CruzSenate Republicans face tough decision on replacing Ginsburg Cruz: Trump should nominate a Supreme Court justice next week Renewed focus on Trump's Supreme Court list after Ginsburg's death MORE (Texas), the other freshman senator running for the GOP nomination.

Bush’s exit after the South Carolina primary created an air of optimism for the Rubio campaign. The GOP establishment hates Trump and Cruz, and Rubio’s head-to-head numbers against Clinton were strong.

The likable, though heavily scripted, Rubio finished a strong third in Iowa. His advisers reportedly devised a 3-2-1 strategy where he would follow up his Iowa showing with a second-place finish in New Hampshire and a win in South Carolina.

But he stumbled badly in New Hampshire, finishing fifth after a dismal debate performance where New Jersey Gov. Chris Christie portrayed him as a talking-point robot. Since then, Rubio has struggled for traction. Now he is on the precipice of what could be a humiliating defeat in Florida, where it’s possible he could fall behind Cruz, to third place.

It arguably would be the worst home-turf defeat in politics since Al Gore Albert (Al) Arnold GoreFox's Napolitano: 2000 election will look like 'child's play' compared to 2020 legal battles Who calls an election? Why we need patience and nonpartisanship this time Universal mail-in voting jeopardizes the equal right to vote, but absentee voting protects it MORE lost Tennessee in the 2000 presidential race. After also losing the contested general election, Gore said he was headed home to “mend some fences, literally and figuratively.”

Other 2016 GOP White House hopefuls, including Sens. Lindsey Graham Lindsey Olin GrahamSenate Republicans face tough decision on replacing Ginsburg Democratic senator calls for eliminating filibuster, expanding Supreme Court if GOP fills vacancy What Senate Republicans have said about election-year Supreme Court vacancies MORE (S.C.) and Rand Paul Randal (Rand) Howard PaulSecond GOP senator to quarantine after exposure to coronavirus GOP senator to quarantine after coronavirus exposure The Hill's Morning Report - Sponsored by National Industries for the Blind - Trump seeks to flip 'Rage' narrative; Dems block COVID-19 bill MORE (Ky.), bowed out of the race before constituents in their home states voted.

Rubio and his campaign have predicted victory in Florida for weeks. If he triumphs, Rubio would win all 99 delegates in the winner-take-all state and attract massive momentum.

But few think he can pull off the upset in his own backyard.

“It’s not a matter of do or die — it’s done,” Florida Republican strategist Chris Ingram said. “If you believe the polls, all are consistently, except one, showing him losing in double digits. How do you overcome that? Can that many polls be wrong?”

Since his second-place finish in the Nevada caucuses, Rubio has failed to finish above third place in 17 of the 21 subsequent contests.

He reworked his campaign message for a time to go after Trump with personal attacks, suggesting the real estate mogul had wet his pants and making a reference to Trump’s “small hands.”

It didn’t work, as Rubio later acknowledged, and he said he regretted making the comments.

He endured a terrible night on Super Tuesday and even worse results the following week, amid rumors he would drop out of the GOP race before Florida.

Rubio instead decided to make a last effort to win the Sunshine State, but his fundraising will dry up if he can’t pull out a miracle victory.

It is unlikely Rubio would be picked as Trump’s or Cruz’s running mate, partially because of his work on bipartisan comprehensive immigration reform. The party’s base has panned that bill, and his association with it could hamper future Rubio campaigns as well.

A loss on Tuesday would send Rubio back to the Senate, where his return as a lame-duck member would be less than glamorous. Trump and other candidates have slammed Rubio repeatedly for skipping Senate votes to attend to his presidential run.

Rubio could try to run for governor in 2018, but a devastating defeat in Florida Tuesday would make that much harder.

“It’s a huge embarrassment not to win your state outright when there are, not counting Trump as a Floridian, no other Floridians in the race,” Ingram said.

“While it’s not the whole story, it’s something of a referendum on him,” he added.

Many think the young senator could turn to the private sector or political punditry, two paths that could be lucrative and that would also not cut off a political comeback. Rubio is not wealthy, having cashed out a retirement fund in 2014 to help pay for his kids’ education.

Even if Rubio loses Florida, many think he will be back in the political arena.

“He is such a young candidate,” GOP strategist Ron Bonjean said. “He has a big career in politics ahead of him, and this should not stop him.”