MIAMI —  Sen. Marco Rubio cast himself as the forward-looking candidate to lead the nation toward a new American century when he announced his presidential bid Monday, framing the election as a “generational choice” for Americans.

“Grounded by the lessons of our history, but inspired by the promise of our future, I announce my candidacy for President of the United States of America,” Rubio told supporters at Miami’s Freedom Tower.

Rubio’s candidacy will lean heavily on his personal story as the son of Cuban immigrants and argue that the American Dream seems unattainable for many because “too many of our leaders and their ideas are stuck in the twentieth century.”

“My candidacy might seem improbable to some watching from abroad,” Rubio said. “In many countries, the highest office in the land is reserved for the rich and powerful. But I live in an exceptional country, I live in an exceptional country, where even the son of a bartender and a maid can have the same dreams and the same future as those who come from power and privilege.”

The speech marks the official public launch of a long-awaited campaign for the 43-year-old freshman senator, and signals he’ll aim to turn his youth and relative inexperience into a central calling card of his campaign.

The senator told supporters in a conference call earlier Monday that he planned to launch his campaign, an aide tells CNN, but he’ll spend at least part of this week focused on his work in the Senate. Rubio plans to head back to Washington on Tuesday for the high-profile Senate Foreign Relations Committee markup of a bipartisan bill requiring congressional approval for any Iranian nuclear deal.

An aide tells CNN on Thursday he’ll head to New York City for fundraisers before traveling to New Hampshire on Friday for the Republican Leadership Summit, where he’ll stand alongside most of the rest of the announced and prospective GOP presidential field as an official contender for the first time.

But while Rubio has all the makings of a winning presidential candidate — youth, a compelling personal narrative and deep roots in a crucial swing state — he’s missing one thing: Support.

Rubio consistently polls in the middle of the GOP primary pack, trailing fellow Floridian Jeb Bush, Wisconsin Gov. Scott Walker and even more conservative alternatives like Texas Sen. Ted Cruz.

Rubio has all the makings of a winning presidential candidate: Youth, a compelling personal narrative and deep roots in a crucial swing state. But as he unveils his presidential campaign, he’s missing one thing: Support.

Rubio consistently polls in the middle of the GOP primary pack, trailing fellow Floridian Jeb Bush, Wisconsin Gov. Scott Walker and even more conservative alternatives like Texas Sen. Ted Cruz.

“I do think he’s going to try to reach the American people in a way that tells a story of a very different, optimistic, prospective vision for America, that isn’t just the doom and gloom that we tend to get an awful lot of the time on our side,” said Florida GOP strategist Rick Wilson.

Rubio is the third Republican to officially announce a campaign for the presidency, joining Sens. Ted Cruz of Texas and Rand Paul of Kentucky. The field is sure to expand in the coming months as Bush, Walker, New Jersey Gov. Chris Christie and others eye the race for the White House.

“There’s a lot of static in the air right now,” Wilson noted, alluding to the launch of Democratic front-runner Hillary Clinton’s campaign on Sunday.

“But I also think that Marco Rubio has a certain fluency, and ability to connect with voters, and this will be one of the first times a wider audience has seen it. When people who haven’t seen Marco speak finally see Marco speak, they stand back and say, ‘Whoa — what have I been missing?'”

That eloquence alone won’t win him the primary, however, and Rubio now faces the challenge of maintaining establishment interest while growing his appeal among conservatives.

The right remains wary of Rubio for partnering with Democrats on an ultimately failed immigration reform bill after riding into office on the 2010 tea party wave.

Just right

But in the middle is just where Rubio wants to be.

He’s hoping to carve out a path in the crowded GOP field as the candidate who’s not too far right to lack credibility nationally, and yet not too squishy on conservative priorities like guns and same-sex marriage to lose the GOP base.

Rubio has eschewed the bomb-throwing of conservatives like Cruz and Louisiana Gov. Bobby Jindal, and the head-spinning vacillations of some of the party’s more establishment-minded candidates in favor of what supporters see as a candid pragmatism.

He was the first in the 2016 field to declare, without reservations, that parents “absolutely” should vaccinate their children. On same-sex marriage, he said if the Supreme Court rules it’s constitutionally protected, “we have to abide” by that ruling. He repeatedly asserted that it was impossible to defund President Obama’s immigration executive order by shutting down the Department of Homeland Security.

That strategy means he may not win any of the early nominating states that typically winnow down the field, but the senator and his advisers are banking on top-three finishes that keep him in the game until the flaws in the rest of the field are apparent and voters are looking for another option.

But it doesn’t come without risks. One of Rubio’s biggest obstacles to the nomination remains a persistent skepticism among conservatives who believe he sold out by taking a lead role in negotiating the 2013 immigration reform bill, which died in the House after Rubio helped secure its passage in the Senate.

In doing so, he plummeted from tea party darling and GOP rising star to freshman has-been in a matter of months, facing hecklers at town hall meetings and declining approval ratings in his home state.

Still, he’s made light of the controversy, joking at a February event that he’s the rare elected official to be heckled “by both sides of the immigration debate.” And the gambit won him enduring respect among many establishment Republicans, who admire his willingness to compromise and cut deals.

Foreign policy prowess

Where Rubio has seized the spotlight, however, he’s made it count.

Rubio led the charge earlier this year against the Obama administration’s move to thaw relations with Cuba, appearing on nearly every major news network to slam the policy shift as shortsighted and scheduling hearings as chairman of the Senate Foreign Relations Western Hemisphere Subcommittee on the issue.

The potential advantages for Rubio in the Cuba issue were varied. It allowed Rubio to introduce himself to an entirely new audience of Americans, as the historic policy shift drew front-page headlines nationwide. It gave him an opportunity to emphasize his compelling personal narrative as the son of Cuban immigrants who left the country due to many of the same hardships imposed by the Castro regime that Cubans continue to experience today.

And it was yet another chance for Rubio to stake a claim as the GOP’s strongest candidate on foreign policy, which Republicans believe will become a defining issue in the primary and general elections.

While Rubio hopes to wind his way down the middle of the GOP, he and his advisers believe foreign policy will be his calling card in the 2016 election: The issue that piques voters’ interest keeps them coming back.

The freshman senator has been working since his early days in office to build the experience to make that case. He’s taken 12 trips abroad since 2010 and co-sponsored more than a dozen bills on issues ranging from Russia’s aggression against Ukraine to humanitarian crises in Haiti. He is a frequent and prominent critic of Obama’s plan to tackle ISIS, and has slammed the Iran deal as insufficient to prevent the nation from gaining nuclear weapons.

Rubio has weekly briefings on foreign policy issues with leading advisers in the party, and aides say he’s a voracious reader of policy papers and international news.

Sunshine State showdown

But first, he’ll have to maneuver his way through the rocky and complicated primary terrain, and his launch puts him on a certain collision course with another Florida politician: former Gov. Jeb Bush.

Bush holds a slight lead over the field in early polling and remains the preferred pick for most of the GOP’s establishment wing, and has already locked up a sizable chunk of the party’s big donors, despite being still weeks away from announcing.

With Florida moving to a winner-take-all primary system, the Sunshine State showdown on March 15 could prove to be a pivotal contest for both candidates, and Bush’s team is reportedly already strategizing to lock up the state’s primary vote.

But Rubio’s already shown that Bush will be less of an obstacle than many initially expected, as he’s managed to post strong fundraising totals despite competing with Bush for hometown dollars.

Before Rubio makes it to Florida, however, he’ll have to stay in the game for the party’s early nominating contests. Though he’s not yet the clear pick for voters in Iowa, New Hampshire or South Carolina, he’s hired a top-notch team of strategists to steer him through the primaries there.

Those include Todd Harris, a Rubio campaign strategist, who advised Jeb Bush in the early 2000s before helping drive Rubio to an upset Senate victory in 2010; Terry Sullivan, who’s running Rubio’s PAC and previously ran former South Carolina Sen. Jim DeMint’s campaign; and Jim Merrill, Mitt Romney’s New Hampshire guru, who’s serving in the same role for Rubio.