The party’s big donors have made clear their distaste for the former president. Now, as he barrels toward the nomination, they are reacting with a mix of hand-wringing, calls to arms and fatalism.

On Labor Day, Eric Levine, a New York lawyer and Republican fund-raiser, sent an email to roughly 1,500 donors, politicians and friends.

“I refuse to accept the proposition that Donald Trump is the ‘inevitable’ Republican nominee for President,” he wrote. “His nomination would be a disaster for our party and our country.”

Many of the Republican Party’s wealthiest donors share that view, and the growing sense of urgency about the state of the G.O.P. presidential primary race. Mr. Trump’s grip on the party’s voters is as powerful as ever, with polls in Iowa and New Hampshire last month putting him at least 25 percentage points above his nearest rivals.

That has left major Republican donors — whose desires have increasingly diverged from those of conservative voters — grappling with the reality that the tens of millions of dollars they have spent to try to stop the former president, fearing he poses a mortal threat to their party and the country, may already be a sunk cost.

Interviews with more than a dozen Republican donors and their allies revealed hand-wringing, magical thinking, calls to arms and, for some, fatalism. Several of them did not want to be identified by name out of a fear of political repercussions or a desire to stay in the good graces of any eventual Republican nominee, including Mr. Trump.

“If things don’t change quickly, people are going to despair,” Mr. Levine said in an interview. He is among the optimists who believe Mr. Trump’s support is not as robust as the polls suggest and who see a quickly closing window to rally behind another candidate. In Mr. Levine’s 2,500-word Labor Day missive, he urged his readers to pick Senator Tim Scott of South Carolina.

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Other schools of thought exist. Some donors have backed Mr. Trump’s rivals despite believing that he is unbeatable in the primaries. These donors are banking, in part, on the chance that Mr. Trump will eventually drop out of the race because of his legal troubles, a health scare or some other personal or political calculation.

Fred Zeidman, a Texas businessman who is an enthusiastic backer of Nikki Haley, the former South Carolina governor, said he had given her a blunt assessment of her prospects last month.

“You’re at 2 percent, and he’s at 53 percent,” he recalled telling her, in only a slight exaggeration of Mr. Trump’s polling advantage. “He ain’t going to erode that much. Something needs to happen to him for you to overtake him.”

Privately, many donors said that the primary contest so far — especially the first Republican debate last month, in which Mr. Trump did not take part — had felt like a dress rehearsal for a play that would never happen. One donor’s political adviser called it “the kids’ table.”

One Texas-based Republican fund-raiser, who has not committed to a candidate and insisted on anonymity to discuss private conversations, said he regularly told major donors that like it or not, Mr. Trump would be the nominee.

“Intellectually, their heads explode,” the fund-raiser said. He said many donors were “backing off” rather than supporting a candidate, reflecting a fundamental belief that nobody can defeat Mr. Trump.

Large-dollar Republican donors, even those who enthusiastically or reluctantly backed Mr. Trump in 2016 and 2020, have made no secret of their wish to move on in 2024.

Some big donors have stuck with Mr. Trump, though not nearly as many as in past cycles, at least not so far — a super PAC backing Mr. Trump has reported just 25 contributions of $100,000 or more. They include $2 million from the casino magnate Phil Ruffin and $1 million from the former real estate developer Charles Kushner, the father of Mr. Trump’s son-in-law Jared Kushner. Mr. Trump pardoned the elder Mr. Kushner on his way out of office.

Major donors, particularly those in the tier just below the billionaire power players, have seen their influence wane in recent elections, a trend inextricably bound up in Mr. Trump’s continued hold on Republican voters. The explosive growth of small-dollar contributions — a phenomenon that, on the Republican side, has overwhelmingly favored Mr. Trump — reflects a widening disconnect between voters’ sympathies and the interests of big donors.

The conservative commentator Bill Kristol, who has become a pariah in his party over his longstanding opposition to Mr. Trump, said he told donors and their advisers at the beginning of the year that if they were serious about defeating Mr. Trump, they had to spend money in a concerted effort to persuade Republican voters that he should not be the nominee.

The hope was that, by Labor Day, Mr. Trump’s poll numbers would be in the 30s, Mr. Kristol explained. Instead, he said, “they’ve done nothing, and Trump is at 50 percent.”

Mr. Kristol said he was not sure if donors had a kind of “learned helplessness,” or if they were just wary of offending Mr. Trump and his supporters. “I think, ultimately, they tell themselves they could live with him,” he said.

“We know what a world would look like if real conservative elites really decided they wanted to get rid of Donald Trump,” Mr. Kristol said. “And that’s not the world we are living in.”

If there was any hope among big donors that the various investigations into Mr. Trump would undermine his popular support, such dreams have faded. Each successive indictment — four since late March — has brought waves of financial contributions and new energy to his poll numbers.

Some donors expressed incredulity that Mr. Trump would be able to run for president while fighting off the charges. He faces a busy calendar of trials next year that is likely to grow only more complex.

“I don’t see how he’s going to deal with these huge legal problems,” said the Long Island-based metals magnate Andy Sabin, who is backing Mr. Scott. “I don’t really care about his numbers. I think he’s got enough other stuff going on. All of these trials start — who knows? We are in uncharted territory.”

Mr. Sabin conceded that Mr. Trump had a “very solid base,” adding that he would “almost have to murder somebody” for people to turn on him. “People think he’s God.”

Many major donors, even those who believe Mr. Trump committed crimes and who think his actions surrounding Jan. 6, 2021, were abhorrent, said they believed the indictments were politically motivated. Some also suggested that the indictments had temporarily inflated his poll numbers, by keeping him in the news and fueling voter outrage on his behalf.

“I fundamentally believe Trump’s numbers are artificial,” said Jay Zeidman, a Texas-based health care investor and major fund-raiser for Gov. Ron DeSantis of Florida (and the son of Fred Zeidman). “I’m not saying they are making them up — I don’t think there’s real strength behind those numbers.”

He continued: “I think you have to be patient, and let the gravity of the situation he’s in take hold. This election is not about vindicating one man. This is not a referendum on Trump.”

Mr. Zeidman, like others, said he believed Mr. Trump would lose the presidential race and drag down Republican candidates for Senate and the House. “I believe that Republican primary voters need to understand the opportunity they have to win a very winnable presidential election.”

Dan Eberhart, a private equity and energy executive who is also backing Mr. DeSantis, said that he expected Mr. Trump’s legal troubles to weigh him down, and that he believed most voters were looking for a second choice.

“By the time Super Tuesday comes around, Trump is going to have been beaten in Iowa, and the dam is going to burst,” he predicted. “Once someone else is viable, I think you’re going to see him quickly melt.”

Then, Mr. Eberhart said, donors who have not committed to a candidate will come out of the woodwork: “They are actively holding their breath, wanting a solution to Trump but not knowing what it is.”

As some donors have cast about for a late entrant to the race who could challenge Mr. Trump, the name that comes up most often is Gov. Glenn Youngkin of Virginia.

Mr. Levine addressed the Youngkin question in his essay, saying: “Waiting for someone else to get into the race is not an option.” (Mr. Youngkin has not ruled out a run and has said he is focused on Virginia’s state legislative elections this fall; with each passing day, the logistical barriers to entry grow higher.)

Bill Bean, an Indiana-based real-estate executive and backer of former Vice President Mike Pence, said the field would narrow until there was a “clear alternative” to Mr. Trump.

Mr. Bean backed Mr. Trump’s re-election campaign in 2020, and supported the policy decisions he made as president. “But I would like to see us move forward,” he said. “I want to look at the future in a positive way. I hear that a lot more than maybe the poll numbers show.”

By Rebecca Davis O’Brien

Ruth Igielnik contributed reporting.

The New York Times