A few years later, Rubio was running for commissioner in West Miami at age 26.
Rebeca Sosa, who was a commissioner at the time, said she was gardening at her house when he came to her asking for support and spelled out why he was running for office.
"I wasn't prepared to see such a young person bringing so much meaning, emotion to his answer of why, that I stopped everything I was doing and I told him, 'Let's go and have coffee,'" she said.
"At that age, usually they are thinking about 'party,' they are thinking about 'girlfriend;' and he was thinking about, 'What can I do to pay back to society?'"
Rubio soon got elected to the Florida House of Representatives and within just a few years his colleagues gave him a term as their leader: Speaker of the House.
Taking a steeper path
But his next decision -- to run for Senate -- was not the obvious path, since it meant a daunting primary challenge to a popular governor in his own party.
"Early on, the entire establishment was against Marco," said campaign manager Jose Mallea. "There were some tough times when you couldn't raise money or when folks weren't endorsing you."
Rubio painted Crist as a centrist and appealed to conservatives and tea party voters with his focus on economic opportunity, government spending and the debt.
But Crist had statewide name recognition and a strong fund raising base. And Rubio was not without weaknesses, including his youthful appearance and questions about his use of a Republican Party credit card for personal expenses. Rubio blamed the misuse of funds on a mix up and said he reimbursed the party. But Crist reminded voters in a campaign ad that Rubio was being investigated "for using a Republican Party credit card to pay for flights and meals."
In his book "American Son," Rubio said he considered dropping out of the race early on.
"The only people who thought I could win all live in my house," Rubio recounted in a speech last summer. "Four of them were under the age of 10," he said, referring to his four children.
But his wife persuaded him to persevere, and he won a surprise victory.
His wife, Jeanette Dousdebes, a one-time Miami Dolphins cheerleader, keeps a low profile compared to other political spouses. In a rare interview last year, she told Politico what she thinks of making campaign appearances: "In the future, if I have to do it, of course I'll do it. But in general, I am shy."
Rubio first spotted her at the local recreation center in West Miami just a few blocks from the modest house he grew up in (and a few blocks from where he lives now). He proposed to her on Valentine's Day 1997 at the top of the Empire State Building.
In the Senate, Rubio has several characteristics that set him apart from most of his Republican colleagues.
Unlike most of his colleagues, Rubio is not a wealthy man. He did not grow up with money and soon after he was elected to the Florida legislature he had to give up his car and move into his mother-in-law's house. He still owed significant debt on his student loans when he was elected to the Senate, although thanks to the royalties from his book, he has now paid them off.
Not exactly an NFL prospect
After high school, Rubio earned a football scholarship to a college in Missouri, playing cornerback. He soon transferred back to Florida as the school ran into financial difficulties, and he admits he was never destined to be NFL material. Instead, he jokes about how ironic it is that his wife made it to the NFL but he didn't come close.
Still, when former Miami Dolphins quarterback Dan Marino threw him a few passes on the floor of the Florida House in 2006, with a crowd watching, Rubio showed his stuff -- first making an easy catch, but then also some harder ones.
He is younger than all the other senators, except Mike Lee of Utah, who is a week younger, so he may be mistaken for a junior aide in Capitol elevators.
But he also may have a better sense of younger generations than most of his colleagues. For example, in a recent interview posted on BuzzFeed, the senator offered a detailed discourse on rap and hip-hop. At the risk of offending some of his audience, he compared two top rappers from the 1990s by declaring, "Tupac's lyrics were more insightful -- apologies to Biggie fans." Asked by GQ to name his favorite rap songs, he listed "Straight Outta Compton" by N.W.A., "Killuminati" by Tupac, and Eminem's "Lose Yourself."
But when it comes to religion, he describes himself as a traditional Catholic -- albeit one who also was baptized Mormon when his family converted for a few years while living in Las Vegas. More recently, he has supplemented Catholic Masses by also attending services at a Baptist church in Miami, according to his office.
As soon as he won his Senate race, Rubio drew speculation about potential presidential aspirations and immediate comparisons to Barack Obama.
Like Barack Obama, Marco Rubio is young and well-spoken, comes from an ethnic minority and has only a few years of experience in the Senate. In addition, he came to Washington after serving in his state legislature, as did Obama, and he benefited greatly from a high-profile speaking role at his party's convention in 2012 -- as Obama did in 2004.