Sen. Marco Rubio (R-Fla.) at a Heritage Action for America candidate forum in Greenville, S.C. on Sept. 18, 2015. (Chris Keane/Reuters)

Ten days after Sen. Marco Rubio launched his campaign for president in April, his aides doused cold water on a poll showing him leading the Republican pack. When he won positive reviews in the first debate in August, he retreated to a quiet schedule of raising money and holding small-scale events. Now with one of his chief potential rivals out of the picture, he is again warning against hype.

What seems like a series of missed opportunities is actually the Florida Republican’s playbook: Avoid peaking early, stay on message, and keep out of the daily fray that has eaten other candidates alive.

The strategy may be starting to pay dividends. Wisconsin Gov. Scott Walker, who chased headlines and veered clumsily from one issue to the next, is out, along with former Texas governor Rick Perry. Former Florida governor Jeb Bush has been sidetracked by a nasty feud with Donald Trump.

The latest positive sign for Rubio was a poll released Wednesday that showed him leading Bush 19 percent to 11 percent in their home state of Florida. Trump leads the GOP pack with 32 percent in the Florida Atlantic University survey.

“I think, so far, almost everyone is gravitating to Rubio,” said Virginia developer Bob Pence, referring to bundlers who backed Walker. Pence is a GOP fundraiser who was backing Rubio and Walker.

Since his announcement rally in Miami in April, GOP presidential candidate Marco Rubio has kept his profile relatively low in hopes of a late surge. (Charles Ommanney/For The Washington Post)

But Rubio must clear difficult hurdles. He lacks a clear base of support in the party and faces a difficult path in early-nominating states. He’s a lifelong politico at a moment when the party is embracing outsiders. His sponsorship of a comprehensive immigration reform bill could be a problem for many conservative activists. And when national attention has fallen on him, Rubio hasn’t always handled it well.

His backers say he can overcome such obstacles with a campaign structure designed to let his natural political skills show — and shut out just about everything else.

“He can relate to people in a different manner than any of the politicians we have seen,” said Frank VanderSloot, a top Republican donor who has narrowed his choices to Rubio or former Hewlett-Packard chief executive Carly Fiorina, with Bush a distant third.

Rubio, 44, has stuck to his pitch as a new-generation leader — to the point that he sounds like a broken record. His team of paid staffers is relatively small, estimated to be between 40 and 50, compared with the 90 that Walker had. Rubio’s polling averages have kept him near the top of the non-outsider pack.

“You want everybody looking at you as the next president in February and March,” said J. Warren Tompkins, who runs Conservative Solutions, a pro-Rubio super PAC. “It takes a lot of discipline to understand that. You get pressure from inside the campaigns. You get pressure from the Washington financial people.”

On Sunday, Rubio’s campaign sent out a news release saying “Marco Dismisses New Poll Numbers,” referring to a CNN survey that had him climbing to fourth place.

After Walker’s collapse amid personnel drama and heavy debt, Rubio is beginning to look like a welcome change of pace for some of Walker’s top donors. Walker financiers Stanley S. Hubbard and Eric Anton told The Washington Post this week that Rubio is on their short lists of favorite candidates.

Sen. Marco Rubio, who's running for president, is known for his stances on immigration and tax reform. Here's the Florida Republican's take on Obamacare, the Islamic State and more, in his own words. (Julie Percha/The Washington Post)

While Bush has dominated the money chase with a super PAC that has raised record sums, Rubio is trying to make the most of limited resources. He had the most cash in his campaign account of any GOP candidate at the midpoint of the year and has been spending his money slowly, campaign finance reports show.

Rubio’s supporters say his biggest assets are his youth, his communication skills and his biography as the son of Cuban immigrants. His “New American Century” campaign theme is meant in part to be an implicit contrast with Bush and Democratic candidate Hillary Rodham Clinton.

Rubio’s campaign does not authorize staff profile stories. It does not send out news releases announcing new paid staff members. Campaign officials rarely talk about tactics publicly. Rubio’s campaign manager, Terry Sullivan, declined to comment on strategy for this story.

The campaign has also been notably risk-averse on many political issues. Rubio has mostly taken orthodox Republican positions on domestic and foreign matters and has generally declined to engage his competitors in political combat.

“They haven’t gone out on a limb a single time,” said a senior Republican in regular contact with the GOP campaigns. The Republican, granted anonymity to speak candidly, argued that Bush has taken a chance by deciding to fight Trump.

The biggest risk of Rubio’s Washington career was joining a bipartisan group of senators who pushed a sweeping immigration bill that included a path to citizenship for undocumented immigrants. The bill died in the GOP-controlled House amid a conservative backlash.

Rubio has sought to distance himself from the proposed legislation, saying he now supports a piecemeal immigration plan that begins with border security and enforcement before potentially offering a path to citizenship for undocumented immigrants.

But with Trump running on a hard-line immigration platform that has electrified the conservative base, Rubio’s past could haunt him. The real estate mogul labeled him “Senator Marco ‘amnesty’ Rubio” on Twitter on Tuesday night.

Another challenge is Sen. Ted Cruz (R-Tex.), who voted against the immigration bill Rubio pushed. Cruz has signaled that he intends to aggressively contrast his immigration record with that of his competitors. The tea party favorite, who attracted more campaign and super-PAC money than Rubio through the end of the second quarter, also stands to do well with former Walker donors, Republicans said.

While conservative activists and evangelical Christians are Cruz’s base, Rubio doesn’t really have one. He also lacks an obvious route to victory through the early-voting states.

The past two Iowa winners have been social-conservative warriors. And New Hampshire has a history of contrarian picks.

Rubio must also overcome deep loyalty to Bush in the establishment, Bush’s massive war chest and his appeal in Florida, a potentially make-or-break state for Rubio in the primary.

Another question is how Rubio will fare under increased scrutiny. Democrats have zeroed in on him since last week’s GOP debate, slamming him for saying that women are “pushed into abortions” by Planned Parenthood for fetal tissue and knocking him for raising money on Yom Kippur at the home of a wealthy art collector who owns paintings by Adolf Hitler.

Early in his campaign when he was receiving heavy national attention, Rubio ran into trouble when he gave muddled answers to questions about whether the United States should have invaded Iraq, including during a live Sunday news show appearance.

The plan by Rubio’s campaign and the super PAC supporting him is to raise his profile shortly before the first votes are cast in early-nominating states. Both have made a substantial investment in TV ads later this year and early next year.

Speaking at an event this week hosted by National Review, Google and YouTube, Sullivan, Rubio’s campaign manager, summed up his view by singling out candidates who were leading at this point in previous races before flaming out.

“There’d be nothing worse in my mind than being in first place right now,” he said.

Matea Gold contributed to this report.