Rivals to Donald J. Trump and their strategists told financiers that time is running out to build up a viable alternative to the former president.With less than 100 days until the Iowa caucuses, Donald J. Trump’s leading rivals continue to engage in a pitched battle with one another as much as with him, igniting fears that internal divisions were threatening to doom efforts to find a fresh face for the Republican Party in 2024.From Dallas to Park City, Utah, top Republican donors gathered behind closed doors this week as talk intensified about the need to cull the G.O.P. field. In private remarks to donors in Utah, Nikki Haley, the former ambassador to the United Nations, delivered a blunt message that it was time to pick sides and invest if there was any chance to prevent another Trump nomination.“Get in the game,” Ms. Haley urged them, according to two people who were present at the event.But given Mr. Trump’s durable lead, some political financiers are considering staying on the sidelines. For those donors who aren’t, the choice has increasingly narrowed to Gov. Ron DeSantis of Florida and Ms. Haley, whose fortunes have been lifted by her performance in the first two debates. Senator Tim Scott of South Carolina is a factor as well, given the $25 million his super PAC has remaining in television ad reservations in Iowa, New Hampshire and South Carolina in the next three months.On Friday, teams of advisers to Mr. DeSantis, Ms. Haley and Mr. Scott descended on Dallas for separate presentations to an exclusive gathering of some of the most influential Republican donors in the nation, a group known as the American Opportunity Alliance. They met at a property owned by the billionaire Republican financier Harlan Crow, who has gained attention and scrutiny for his close relationship with Justice Clarence Thomas.The crowd included some of the party’s biggest contributors or their top representatives, megadonors like Paul Singer and Ken Griffin who can spend tens of millions of dollars. And the stakes produced pointed presentations, according to more than a half-dozen people who were in the room or had been briefed on the remarks.The DeSantis team argued that any effort to push him out of the race would backfire for the anti-Trump cause. Three top DeSantis campaign strategists — James Uthmeier, David Polyansky and Ryan Tyson — presented internal polls showing that 90 percent of his supporters would drift to Mr. Trump if Mr. DeSantis were to exit the race. Ms. Haley’s supporters, they said in contrast, would flow to Mr. DeSantis if she departed.The DeSantis team suggested that Mr. Trump had to be stopped in Iowa, and that Mr. DeSantis was the only one positioned to do so. And they acknowledged Mr. DeSantis’s past struggles, describing themselves as having fought back to a stronger position.Gov. Ron DeSantis in Nashua, N.H., on Friday. His team has told donors that any effort to push him out of the race would backfire on the anti-Trump cause.John Tully for The New York TimesMs. Haley’s advisers, Betsy Ankeny and Jon Lerner, showed their own internal surveys, which placed Ms. Haley ahead of Mr. DeSantis in New Hampshire and South Carolina and had the two of them tied in Iowa. Mr. DeSantis had stalled, they argued, and she was rising.In a sign of the threat Ms. Haley poses to Mr. DeSantis, Never Back Down — the leading pro-DeSantis super PAC — is readying an anti-Haley ad campaign and has tested several attacks, including her ties to China, according to a person familiar with the matter. Such a move would be a watershed moment, as DeSantis advisers have long insisted the primary is a two-man contest between the governor and Mr. Trump.Mr. Scott, whose team had not initially been invited to Dallas, was represented by Jennifer DeCasper, Zac Moffatt and Erik Iverson. They revealed that Mr. Scott would enter October with $11.6 million cash on hand for the primary — more than either Mr. DeSantis or Ms. Haley.Ms. DeCasper pitched Mr. Scott’s toughness and his willingness to stand up to Mr. Trump. She invoked when he confronted Mr. Trump for the former president’s equivocations after the white supremacist violence in Charlottesville, Va.“We’ve never flown to Mar-a-Lago to kiss the ring, to ask permission for anything,” she said.The dueling presentations underscored the degree to which the race to be the main alternative to Mr. Trump is playing out in donor meetings as much as on the ground in the early states.Ms. Haley, campaigning in New Hampshire on Friday, made explicit the power of wealthy donors to narrow the field. “I think it’s up to the voters, and I think it’s up to the donors to decide which candidates should get off the stage,” Ms. Haley said as she filed to appear on the ballot in the state.For months, donors have had private discussions not just about the possibility of collectively backing a single alternative to Mr. Trump, but whether wealthy backers of low-polling candidates could encourage those candidates to drop out to consolidate anti-Trump support.In recent days, Ms. Haley and Mr. DeSantis have made a series of announcements pitching political insiders on their respective momentum. Mr. DeSantis on Thursday announced his first ad reservation of the race, saying he would spend $2 million in Iowa. That came a week after he started shifting one-third of his staff from Tallahassee to Iowa to bolster his operation in the state.Ms. Haley rolled out her fund-raising haul, revealing she had more cash on hand for the primary than Mr. DeSantis, $9.1 million to $5 million. She also announced the opening of her first office in Iowa and the addition of two staff members in the state, bringing her total to four.For veterans of the 2016 primary, the obsessive focus on the race to be in second place is inflicting a serious sense of déjà vu.“In October of 2015, you had Jeb Bush machine gunning Marco Rubio and Rubio going after Ted Cruz, and nobody was really laying a hand on Trump,” said Alex Conant, a Republican strategist who was a top adviser to Mr. Rubio at the time.“It’s shaping up to be a repeat of 2016,” Mr. Conant added of the current contest. He said that this time, it was even worse for the Trump challengers. “Now, even if you combined everyone’s poll numbers that was on the debate stage, you’d still be under Trump.”A recent national poll from Fox News showed Mr. Trump at 59 percent, virtually unchanged from September. Mr. DeSantis was the next closest at 13 percent, with Ms. Haley in third, with 10 percent.Still, most of Mr. Trump’s rivals tread cautiously when it comes to criticizing the former president.On Monday, Mr. DeSantis made his first appearance on MSNBC, the type of network he had spent years deriding as “corporate media,” a sign of his need for political oxygen and coverage. And while he swiped at how a Trump nomination would be a distraction — citing documents found near toilets in Mar-a-Lago — he evaded a follow-up question about whether Americans should be concerned Mr. Trump was loose with the nation’s secrets, the charge at the center of the special counsel’s criminal indictment.“Well, look, I think that’s an allegation — it remains to be seen,” Mr. DeSantis began, before pivoting to a defense of Mr. Trump.Later in the week, Mr. DeSantis criticized Mr. Trump for his attack on Prime Minister Benjamin Netanyahu of Israel and on Israel’s intelligence services for missing the impending terrorist attack by Hamas. The issue is potent for a number of pro-Israel and politically conservative donors, and Mr. DeSantis’s allies and advisers see it as a Trump vulnerability.Chris Christie, the former governor of New Jersey, said that if donors “don’t pick a candidate, Trump is going to be the nominee.”John Tully for The New York TimesSpencer Zwick, who oversaw Senator Mitt Romney’s fund-raising operation when he ran for president in 2012 and who organized the Utah conference, said Ms. Haley “was probably the strongest in making the case” that donors needed to mobilize to stop Mr. Trump from winning. Other attendees included former Vice President Mike Pence, Gov. Doug Burgum of North Dakota and former Gov. Chris Christie of New Jersey.“If you don’t pick a candidate, Trump is going to be the nominee,” Mr. Christie warned the donors, according to a recording of his remarks obtained by The New York Times.But the lower-polling Mr. Christie urged the donors not to focus on whom they thought could win — “Your track record shows that you don’t” know how to predict that, he said to laughter — but whom they thought would be the best president.“How about we try that one?” Mr. Christie said. More