Nikki Haley Might Challenge Trump in 2024. Other Republicans Aren’t So Eager.

Increased uncertainty is rippling through the Republican Party over how to beat Donald J. Trump for the 2024 presidential nomination, as an array of the party’s top figures move slowly toward challenging the politically wounded yet resilient former president.

Contenders have so far been unwilling to officially jump into the race, wary of becoming a sacrificial lamb on Mr. Trump’s altar of devastating nicknames and eternal fury. Some are waiting to see if prosecutors in Georgia or New York will do the heavy lifting for them and charge Mr. Trump with crimes related to his election meddling after the 2020 contest or hush-money payments to a porn star during the 2016 campaign. And the sitting governors weighing a 2024 campaign, including Ron DeSantis of Florida, are vying to score legislative victories they can use to introduce themselves to voters in Iowa and New Hampshire.

The first entrant against Mr. Trump might be former Gov. Nikki Haley of South Carolina, who served as United Nations ambassador under the former president and is set to announce her candidacy on Feb. 15, according to a person familiar with the plans. And this week, former Gov. Larry Hogan of Maryland said for the first time that he was “actively and seriously considering” running.

But other potential challengers have more quietly wavered over when, where and how to unleash attacks on Mr. Trump’s candidacy, and to begin their own, after a midterm election in which his endorsements failed to usher in the red wave Republicans had expected. Republicans who hope to stop him worry that dithering by possible candidates could only strengthen Mr. Trump’s position — and could even lead to a field that is far smaller and weaker than many in the political world have anticipated.

“There’s a non-Trump lane right now that’s as wide as the Trump lane, and there’s no one in that lane,” Mr. Hogan said in an interview.

The lack of activity has included major Republican donors, a number of whom have moved away from Mr. Trump but, with few exceptions, are keeping their options open.

But a flood of candidates into the race could also help Mr. Trump. Some Republicans fear a repeat of the primary campaign in 2016, when a cluttered field allowed Mr. Trump to win with roughly 25 percent of support in several contests, a possibility that his advisers are hoping for if he faces a particularly strong challenge from any one person.

The case would-be challengers and their aides make behind the scenes is not that Mr. Trump’s policies were wrong, but that he would lose a rematch with President Biden, who won in 2020 in large part by presenting himself as an antidote to Mr. Trump.

Among those who have expressed concern is Paul D. Ryan, the former Republican House speaker, who has called Mr. Trump a “proven loser.” In private conversations, Mr. Ryan has told people that donors and other Republicans need to find ways to ensure that there are not too many candidates splitting the vote against Mr. Trump. But what exact approach they might take is unclear, as is which would-be challengers would be receptive to it.

Mr. Trump has shown signs of both weakness and durability. His fund-raising haul in the first weeks of his campaign was comparatively thin, and members of the Republican National Committee, long a bastion of pro-Trump sentiment, are not eager to back a third Trump campaign. A survey this week by The Bulwark, a conservative anti-Trump website, and the Republican pollster Whit Ayres found that most likely G.O.P. voters wanted someone other than Mr. Trump to be the party’s 2024 presidential nominee.

Yet other recent polls suggest that he remains the Republican front-runner. And the Bulwark survey also found that a staggering 28 percent of G.O.P. voters would be willing to back Mr. Trump in an independent bid, a figure that would all but ensure another four years for Democrats in the White House.

“I think there are a lot of things that are still uncertain” about the 2024 primary race, said former Gov. Haley Barbour of Mississippi, a former chairman of the Republican National Committee.

The clearest example of the mixed Republican situation is Ms. Haley, who has long been seen as a potential presidential candidate. She had made contradictory statements about whether she would challenge Mr. Trump, saying in 2021 that she would not do so. On Wednesday, Mr. Trump posted on his social media site a video of Ms. Haley making that remark, with the taunt that she had to “follow her heart, not her honor.”

Ms. Haley’s expected entrance to the race this month would give Mr. Trump a challenger in the form of a popular former governor from what has historically been the first Southern state to vote in the primary cycle — and a state Mr. Trump won decisively in the 2016 primary.

“I think she could be generational change, and I see that’s the lane Nikki’s got a shot at,” said Katon Dawson, a former chairman of the South Carolina Republican Party who is supporting Ms. Haley.

So far, Ms. Haley appears to be treading gingerly around Mr. Trump. He revealed to reporters over the weekend that she had reached out to him to let him know that she might run — and instead of sounding angry, he sounded almost delighted at the prospect of having a direct target, and a more crowded field.

Others considering a campaign include former Vice President Mike Pence, who has expressed disapproval of Mr. Trump’s efforts to use him to overturn the 2020 election while avoiding most criticism of his onetime ally. Mr. Pence has been building a campaign apparatus, including poaching a staff member from Ms. Haley, but he is not expected to make a final decision on running until later this year.

Another potential Trump rival, former Secretary of State Mike Pompeo, has avoided going directly after his former boss. He has set his sights lower, using his recent book to attack Ms. Haley and John R. Bolton, a former national security adviser under Mr. Trump who is also considering a candidacy.

The person Mr. Trump is most acutely concerned about is Mr. DeSantis, whose advisers in Tallahassee are planning for the state’s coming legislative session with an eye on a potential presidential bid.

The Florida governor, who has a book set to be published this month, has been promoting policies that could translate into applause lines for the Republican primary base, including a proposed “anti-woke” overhaul of the state’s education system and a potential new law letting residents carry firearms without a permit. One change that Mr. DeSantis would almost certainly need from a friendly Republican supermajority in the Legislature: loosening a state law that requires state elected officials in Florida to resign before running for federal office.

Yet while Mr. DeSantis has attracted interest in early primary states, he has a small, insular team, which has concerned some donors and activists. And his lack of a presence in those states has led to questions among activists in places like Iowa and South Carolina about whether he risks squandering a chance to consolidate support if he waits past spring.

Mr. Ayres, the Republican pollster, said that “there’s no question there’s an opening” to run against Mr. Trump.

“In a multicandidate field, he has a lock somewhere around 28 to 30 percent, and that is a very significant portion of the party,” Mr. Ayres said. “And they are very, very committed to him. But if he doesn’t get more than that, in a narrowing field or a small field, he’s going to have a hard time winning the nomination.”

Senator Tim Scott, one of the party’s most prominent Black politicians, is another South Carolinian considering a campaign. He has proved to be one of the most prodigious Republican fund-raisers, collecting $51 million for his re-election campaign last year.

Mr. Scott also laid the groundwork for a national campaign by spending $21 million helping elect Republicans in the 2022 midterms. He endorsed 77 candidates last year and participated in 67 campaign events in 21 states, an adviser said.

This month, Mr. Scott will travel to Iowa, where he will speak at a fund-raiser for the Republican Party of Polk County, and he is beginning a “Faith in America” listening tour, including speeches in his home state and Iowa.

Some prospective candidates have taken on Mr. Trump more directly. Former Representative Liz Cheney of Wyoming, who lost her primary for re-election after helping lead the House committee investigating the former president’s role in the Capitol riot, is said to be considering a campaign, as well as possibly writing a book. Former Gov. Chris Christie of New Jersey has been one of the most vocal Republicans in calling for the party to find a new leader.

And Mr. Hogan has spent the two weeks since he left office speaking with political advisers and donors about running for president. In an interview on Wednesday, he cast the field as one Trump-aligned figure after another aiming to lead a party he said must move beyond the former president in order to win the general election.

“Maybe a crowded field is good, with Trump and DeSantis fighting with each other and with six or eight other Trump people,” Mr. Hogan said. “It might create more of an opportunity for somebody like me.”

Mr. Hogan is not the only Republican without clear Trump ties, however.

Gov. Glenn Youngkin of Virginia has done little to burnish his national profile or prepare for a presidential bid since the midterm elections, when he was a rare Republican welcomed as a surrogate by both moderates and the party’s far right. Back then, he told some Republican allies that he saw an opening if the presidential field was not especially crowded.

Virginia’s legislative session, which runs through the end of February, gives Mr. Youngkin — as it does Mr. DeSantis and Gov. Chris Sununu of New Hampshire — a reason to put off moving forward with presidential planning.