The presidential campaign of Gov. Ron DeSantis is clearly in a downward spiral, whether measured by polling, internal upheaval, shifting strategies or money woes.

Early this year, Mr. DeSantis seemed to have a clear path to the Republican nomination: He was a political fighter in the mold of Donald J. Trump, but without the chaos and with a solid record of conservative achievements in Florida.

But those best-laid plans have met reality — a Trump rebound and a crowded Republican field — and now the Florida governor is desperately struggling to regain his footing after his campaign this week announced its third major shake-up in a month.

In interviews, Republican strategists with experience in presidential races (but unaffiliated with Mr. DeSantis or his 2024 rivals) diagnosed some of the top problems of his campaign.

There is no way around it. Solving the Trump problem is the master key to this election, and no one has found it. Mr. DeSantis, like almost every other Republican in the race, adopted a strategy of never criticizing Mr. Trump, for fear of alienating his ardent base. The theory was that at some point Mr. Trump would disqualify himself, and Mr. DeSantis would be positioned to inherit his supporters.

But now, after three criminal indictments have failed to dent Mr. Trump’s popularity with Republican voters, pressure is mounting on Mr. DeSantis to stop pretending Mr. Trump isn’t in the race and take him on directly.

“The people who want Trump don’t need a mini-me Trump,’’ said Barbara Comstock, a former Republican member of Congress from Virginia, who is not a fan of either the former president or Mr. DeSantis.

This week, Mr. DeSantis took a small step in the direction of taking on Mr. Trump by stating plainly that “of course” he lost the 2020 election, a position that conflicts with what many Republican voters believe.

“Trump is the de facto Republican incumbent, and in order to beat an incumbent you have to give voters a fire-able offense,” said Terry Sullivan, who managed Senator Marco Rubio’s presidential campaign in 2016.

A related problem: Mr. DeSantis has failed to captivate voters, either with a charismatic stump speech or with a new charm offensive in which he wades into crowds, poses for selfies and engages in chitchat. Sarah Longwell, who conducts focus groups of Republican voters, said that recently she had witnessed something novel: Not one G.O.P. voter brought up Mr. DeSantis’s name in the groups. “People are like, we gave you a look and we’re not that interested,’’ she said.

“The No. 1 failing for any campaign, and it’s clearly DeSantis’s problem — what is his elevator pitch?” said Dave Carney, a New Hampshire-based strategist who has advised multiple presidential campaigns.

One day, Mr. DeSantis is reminding voters about taking on the Walt Disney Company over what he views as “woke” corporate meddling. Another day, he is picking a fight with Representative Byron Donalds, the only Black Republican in Florida’s congressional delegation, over the state’s new standards for teaching Black history.

These headline-making fights may break into the Trump-dominated media coverage, but Mr. Carney said they hadn’t given voters a slogan they remember.

“You have to have a message that’s relatable and simple and that you can communicate,’’ he said. “‘Morning in America,’ ‘Are you better off than four years ago?,’ Make America Great Again.’”

Just what that should be, of course, is up for debate.

Mr. Sullivan said he thought Mr. DeSantis was on point when he talks about electability. Mr. DeSantis has often suggested that Mr. Trump, now saddled with criminal charges stemming from his attempt to overturn the 2020 election, can’t win a general election.

“The messaging the other day was very smart — if the election is about January 2021, and not about Joe Biden’s record, we will lose,” Mr. Sullivan said.

Gail Gitcho, a consultant who worked on Mitt Romney’s presidential campaign, said Mr. DeSantis needed to talk about his achievements in Florida.

“He’s got something no one else has — executive experience in a big state with countless examples of his effectiveness and conservatism,” she said. “Stop with the donor-induced shake-ups and run on his record.”

All summer, media reports have been filled with accounts of Mr. DeSantis’s struggles, fed by campaign insiders, his wealthy donors and other Republicans with a close view. It has led to steady headlines about campaign restarts and reboots and a revolving door of personnel. The coverage feeds a narrative of a campaign in trouble, which becomes self-fulfilling.

Mr. Sullivan said Mr. DeSantis needed to just run the plays without discussing them.

“You just have to keep your head down and execute. Win the day. Win the week. Then string them together,” he said.

In an earlier reboot, Mr. DeSantis’s campaign said it would zero in on Iowa, touring the state by bus, after spending hundreds of thousands of dollars on private air travel, and visit all 99 counties. Such a hyperlocal strategy of retail engagement with voters is traditionally what underfunded long shots pursue. But it also raises the stakes for Mr. DeSantis in Iowa, a state where he was trailing Mr. Trump by 24 percentage points in a recent New York Times/Siena College poll.

Although the Iowa caucuses are still several months away, Mr. DeSantis is playing a risky expectations game, one that could make it difficult for him to rebound if he doesn’t post a strong showing in Iowa.

“Clearly, they said they’re going to win Iowa,” Mr. Carney said. “I just think a campaign that talks too much, that brags about what they’re going to do — they set themselves up for traps.”

Ms. Longwell, on the other hand, said an all-in-on-Iowa strategy made sense.

“Iowa is hand-to-hand combat,” she said. “You have to get a story in Iowa that Ron DeSantis is running close to Trump — because now it’s all a downward death spiral.”