Some of Jeb Bush’s donors wonder when he will officially join the race for president, but his camp has a plan. (Ricardo Arduengo/AP)

At a luxury Miami hotel last month, one of Jeb Bush’s chief strategists stood before hundreds of top GOP fundraisers to deliver an unsubtle message: The former Florida governor will not be one of the “presidents of August.”

During his closed-door presentation at the 1 Hotel in South Beach, Mike Murphy dismissed buzz-fueled candidates who rise fast early only to flame out once the primaries begin. Murphy ridiculed the early spate of presidential polls — many of which show Bush lagging, particularly in Iowa — as “noise meters.” And he insisted that the Bush team is patiently playing a long game, one that will not be upended by the actions of his rivals.

Murphy’s talk was aimed in part at quieting pockets of anxiety that have been percolating among Bush supporters who are beginning to worry whether he can excite Republicans in the same way that many of his younger rivals are already doing.

“They are loyal to him and support him, but they’re watching closely to see if he can campaign in a way that says, ‘Yes, he has energy to get the base electrified,’ ” said David McIntosh, president of the conservative advocacy group Club for Growth. He said there is growing “angst” in the Bush bloc of the Republican donor community.

“This isn’t like 1999, when the money decided there is no one else but George W. Bush and watched it all come together,” McIntosh said.

In particular, Bush’s backers wonder when he is going to formally get in the race and start making his case to voters in earnest.

The answer: not any time soon. Bush, who has already stockpiled record sums, intends to hold back from officially declaring his bid for at least another month, people familiar with the plan said.

The strategy is being driven by a confident, tightly knit group of Bush advisers who are focused on amassing as much money as possible for his allied super PAC on the theory that a considerable cash advantage will enable Bush to outlast his competitors.

The approach is similar to the tack Mitt Romney took in 2012, when the former Massachusetts governor prevailed at the end of a protracted primary contest in which a half-dozen candidates briefly tasted front-runner status, only to fall. Romney precipitated many of those falls, using his financial edge to relentlessly attack one opponent after another.

But Bush faces a rougher road to the nomination than Romney did. The Republican field is one of the strongest in years and features several candidates who excite various factions within the party. Many of them will also be supported by their own well-funded super PACs, poised to interject unprecedented money into the race.

Bush, meanwhile, has staked out positions on issues such as immigration and education reform at odds with conservative activists, and his most fervent following rests with the party’s donor class. As the son and brother of former presidents, he must also overcome a feeling among many Republicans that it is time for a fresh start.

Bush had hoped to overcome some of these challenges with his early and aggressive entry as a potential candidate, but he has not been able to have the “shock and awe” impact that some supporters had predicted.

“The big story so far of the Republican presidential race is the failure of Jeb Bush to dominate,” said William Kristol, editor of the conservative Weekly Standard. “He hasn’t pulled it off.”

Bush and his associates maintain they have plenty of time.

“Not announcing yet may look bad to some of our donors,” said Vin Weber, a Republican consultant advising Bush on domestic policy. “They wonder, ‘Gee, are we waiting too long?’ That’s a natural reaction, but it’s jitters. The campaign’s general response is: We have a plan, and we’re on track to achieve all of our goals.”

During a stop Friday at the North Carolina state GOP headquarters in Raleigh, Bush said he will eventually win over voters who have little appetite for another president from his family.

“I have to go earn their respect. I have to go show my heart. I have to talk about my record,” Bush said, adding: “So if I share that, show who I am, have ideas that help people rise up, the dynastic question will subside a bit.”

That is, he noted, if he decides to run — a coy aside that Bush constantly repeats, to the puzzlement of some of his supporters.

The consequences of Bush’s maybe-I-will, maybe-I-won’t attitude are perhaps most apparent in Iowa, which hosts the first-in-the-nation caucuses and has in recent years embraced hard-right favorites.

Unlike his brother, who won the 2000 caucuses after months of charming GOP voters, Bush has so far been less attentive to the state. He plans to attend the Iowa GOP Lincoln Dinner on May 16, but his allies privately acknowledge that he may neglect this August’s Iowa straw poll, a test of organization disliked by national GOP leaders for the attention it showers on lower-tier candidates. Last month, he skipped an Iowa faith group’s summit.

“I don’t care if he’s a Rockefeller liberal. It’s his disdain for the grass roots, our sense that he doesn’t think that Iowa is relevant, that will make people stay away,” said Sam Clovis, a conservative organizer in northwest Iowa.

Douglas E. Gross, a Bush family friend in Iowa who is uncommitted, called Bush’s hands-off manner a “risky” play, especially if the political winds shift and Iowa becomes more important to his chances.

“Caucuses require organizational prowess,” Gross said. “It takes months to develop a turnout effort. As time ticks away, it’s time he won’t get back.”

The Bush operation’s unhurried approach can be traced to Murphy, Bush’s longtime political confidant, who loathes the way the political-media ecosystem in Washington takes daily stock of presidential campaigns. Since the beginning of Bush’s exploration phase, he has cultivated an ignore-the-pundits ethos that brushes aside any momentum at this point in the race as calorie-free fodder for political obsessives.

In his slide-show presentation at the Miami donor conference, Murphy described the months-long money push as necessary to have sizable cash on hand for early next year. So Bush is concentrating now on bringing in tens of millions of dollars for his allied super PAC, taking advantage of the fact that since he is not yet an official candidate, he has more freedom to help raise funds for the independent group.

Murphy also gave donors a glimpse of the campaign’s plans to promote Bush across the ever-changing world of Web platforms and mobile applications. Sounding like a brash Silicon Valley entrepreneur with talk of disruption and innovation, Murphy detailed the operation’s hiring of software developers and designers, attendees said.

The presentation impressed many in the room, who said it is clear Bush’s inner circle has its eyes on a drawn-out race, rather than early gains.

“One of the hardest things in politics is to be patient, to make the plan and work the plan,” said Theresa Kostrzewa, a Republican lobbyist and fundraiser in North Carolina.

Still, there was a persistent reminder throughout the two-day donor meeting of Bush’s odd status as a quasi-candidate, as he and his advisers repeatedly emphasized “if” he runs.

For some donors antsy for him to jump in, the refrain grew old. “It’s like, what’s your problem, what are you waiting for?” said one financier in attendance who requested anonymity to describe the private event.

One of the risks Bush faces in holding back is that he will give a rising star a chance to gain ground — particularly Sen. Marco Rubio, a fellow Floridian.

If Rubio “actually takes hold nationwide, I think Bush is going to have a very difficult time competing with that,” said Saul ­Anuzis, a former Michigan ­Republican Party chairman who is backing Sen. Ted Cruz of Texas. He said Rubio presents a direct threat to Bush’s status as the “most ­acceptable establishment, moderate-conservative candidate.”

For now, no GOP contender holds a clear lead in the early nominating states, with Bush, Rubio, Wisconsin Gov. Scott Walker, Sen. Rand Paul of Kentucky and, occasionally, others clustered near the top. A Quinnipiac University poll of Iowa Republican voters released Wednesday showed Bush a distant seventh, behind neurosurgeon Ben Carson and winning just 5 percent of the vote.

The most vexing challenge for Bush, party operatives said, is that the political tides are against him at a time when Republicans are assessing who would be well-positioned against the expected Democratic nominee, Hillary Rodham Clinton.

“I don’t think he has made many missteps,” Kristol said. “What he’s struggling with is something more structural: The primary electorate is more averse to signing on to an establishment front-runner than they have been in past election cycles. They sense he maybe wouldn’t be the best nominee against Clinton and want someone brash, someone new.

Behind Bush’s careful navigation is also a sense that he needs time to acclimate himself to the rigors of a modern presidential campaign after more than a decade out of politics. Instead of holding rallies, he has mostly been hosting small events and giving low-key talks to donors and Republican groups.

Ron Kaufman, a former Romney adviser who is uncommitted, observed that Bush has a steeper ramp-up than Romney, whose 2012 bid came four years after his first White House run.

“Jeb has not run in 14 years, and he’s getting his sea legs,” Kaufman said . “Even if you’re Roger Clemens, if you were retired for 14 years, it’s hard to come back and immediately pitch in the World Series.”

Scott Clement contributed to this report.