On Tuesday, that image -- along with Rubio's political career -- is at stake.
Rubio, who began his White House campaign 11 months ago as a hero of Florida Republicans, now faces the prospect of defeat in his home state. For years, Republicans believed that Rubio was destined to be a presidential nominee and that even if he fell short in 2016, he would be well-positioned to run for governor in 2018.
A loss of that magnitude could be devastating to Rubio, and leave him in a tough spot if he ever wanted to seek public office again.
Of course, Rubio could eke out a surprise win in defiance of the polls, as Bernie Sanders did in the Michigan Democratic primary last week. For his part, Rubio has insisted he will win. But as he traveled across the state making his final appeal to voters, he hardly exuded the swagger of a candidate in his home state, and grudgingly confronted questions about his intentions after Tuesday.
"January of next year, I will either be president of the United States or I will be a private citizen. If I never hold elected office again, I'm comfortable with that," Rubio told CNN at a press conference in West Palm Beach. "I can't tell you what's going to happen two to four years from now but I have no plans, no thoughts, no contemplation, no meetings, nothing, about any future political run of any sort."
For starters, some Rubio backers said he should end his campaign if he loses Florida.
"We're the backbone -- at least we're supposed to be -- and if he doesn't have the backbone, he can't have a body," said Amethyst Ditieri, a 22-year-old Rubio supporter who attended a campaign event in Orlando on Sunday.
Setting aside his national ambitions, even some former Rubio allies say that he might struggle to re-enter Florida politics if he loses the primary by a wide margin.
Taking a toll on Rubio's standing
His presidential campaign, they say, has taken a toll on his standing in the state. The rift between Rubio and former Florida Gov. Jeb Bush could be problematic in a future campaign, and the time Rubio has spent away from the state has come at a price.
Speculation about Rubio's future has focused on the 2018 race for governor, when Rick Scott will be term limited. Winning the governorship could position Rubio for a comeback in national politics.
But several other Republicans have been circling the race, and it's unclear whether Rubio still has the political strength at home to dominate a statewide race.
Will Weatherford, a former Florida House speaker, who is seen as a possible future candidate for the governorship or the Senate, told CNN this week that Rubio was a "gifted" politician with many doors open to him in Florida politics.
But, he said he did not believe Rubio could crowd other Republicans out of an open-seat race.
"There are other people that would and are considering that seat," Weatherford said. "If he ran, he would be extremely viable, but I certainly don't think he would clear the field."
Preserving his legacy
In what could be the final days of his presidential campaign, Rubio has seemed determined to preserve his legacy.
After briefly adapting Trump's strategy of lobbing personal -- and at times juvenile -- attacks on the campaign trail, Rubio quickly reversed course, saying he regretted his decision to reciprocate Trump's style. Casting aside insults about the color of Trump's hair and the size of his hands, Rubio has returned to the forward-looking message that has fueled his White House campaign since its launch.
He delivered a strong performance at CNN's presidential debate in Miami on Thursday, arguing that Trump's rhetoric isn't presidential. When the billionaire said he didn't want to be "so politically correct," Rubio responded with one of his most memorable lines of the night: "I'm not interested in being politically correct. I'm interested in being correct."
And by Monday night, he struck a decidedly reflective note.
"My whole life, I have been told being humble is a virtue," he said during a speech in West Palm Beach. "And now, being humble is a weakness and being vain and self-absorbed is somehow a virtue."
The gradual deterioration of Rubio's presidential campaign has exposed hard feelings toward the first-term senator within Florida's political circles.
Tampa mayor Bob Buckhorn, a Democrat who has expressed interest in running for governor, said losing Florida on Tuesday would be the ultimate repudiation of Rubio by his own constituents. Buckhorn has vocally criticized Rubio in recent weeks for being inattentive to Florida while he has pursued national office.
"He's never really taken the time to establish real relationships and real roots in Florida and has literally been running for president since the day he took office. I don't just say that as a Democrat," said Buckhorn, who complained that he has never once met Rubio. "There are folks on the Republican side who echo the same sentiments."
Rubio vs. Bush
Further complicating Rubio's relationship with Florida Republicans and donors is his decision this cycle to mount a direct challenge to Bush, his former mentor.
Florida insiders say there is a raw sense of betrayal among Bush allies towards Rubio, and that the bad blood between Bush loyalists and the Rubio camp could interfere with the senator's future aspirations in the state.
Since ending his White House campaign last month after a disappointing finish in South Carolina, Bush has remained out of the public spotlight. Sources close to the former governor say he is unlikely to make an endorsement ahead of the Florida contest.
But Rubio's allies insist that even if Rubio loses to Trump in Florida on Tuesday, voters will ultimately be forgiving. They say it is clear that there are unprecedented emotions fueling the 2016 election and that the Trump campaign, too, is an extraordinary phenomenon.
"What you're seeing is an angry public," said former Florida state Sen. Ellyn Bogdanoff, who is supporting Rubio's campaign.
Trump is "talking their language right now and a segment of the population is very attracted to that," she continued. "Is it the best for our future in terms of our governance? That's yet to be seen. But it's all about timing. It's all about timing."
Over the weekend, Rubio delivered a sober speech at Temple Beth El in West Palm Beach, expounding on the importance of the U.S.-Israeli relationship. He warned that if Trump wins the presidency, his intentions of "forcing Israel to the negotiating table" only "weakens Israel and only further emboldens their enemies."
The temple's rabbi, Leonid Feldman, said the speech was emblematic of Rubio's raw political talent and boundless future potential.
"He is clearly a leader, he has charisma, he has knowledge. He could be -- who knows -- maybe whoever it is, let's say it is Donald Trump. Maybe he'll go back to Little Rubio and say he'll be his national security adviser," Feldman said. "What we're witnessing now is unprecedented in American history. Really."