Nestled in the neo-Georgian sanctuary of the Knickerbocker Club, one of New York’s oldest and fustiest social establishments, a select group of Republican donors gathered late last month to take up an unexpected task: reconsidering Ted Cruz.

Eager to defeat Donald Trump, they seemed willing to overlook a few things: Cruz’s fiery attacks on Wall Street and “special-interest billionaires,” and his swipes at eminent party leaders and lawmakers. But one wealthy financial executive had a question: What did you mean when you attacked Trump for having “New York values”?

“I didn’t mean to attack people in New York,” Cruz, a senator from Texas, said, explaining that he had been criticizing the state’s policies, not its populace. “I love New York.”

Of all the teeth-gritting alliances being forged over opposition to Trump’s rampaging bid for the Republican presidential nomination, few are as unlikely as the emerging bond between Cruz and his party’s elite donor establishment.

Since Cruz’s election to the Senate in 2012, many traditional Republican donors have spurned him, viewing him as a hopeless ideologue whose antics — particularly his leading role in the 2013 government shutdown — damaged the party in service of his ambitions.

But in recent weeks, at small events from the Upper East Side of Manhattan to the Republican precincts of Newport Beach, Calif., they are learning to love Cruz.

“That was then,” said Anthony H. Gioia, a Buffalo, N.Y., businessman and ambassador to Malta under President George W. Bush who expects to meet with Cruz in the coming weeks. “And now is now.”

Bolstered by Cruz’s overwhelming win in Wisconsin on Tuesday, his campaign is moving aggressively to take advantage of the thaw, reaching out to some of the party’s most prominent donors to seek a hearing. Many — though not all — said they were now far more inclined to take the senator’s calls. Former backers of Jeb Bush and Sen. Marco Rubio of Florida have hosted fundraising events or meet-and-greets for Cruz, even while some privately concede that they have their doubts about his temperament.

“Lots of people are giving him a second look,” said John A. Catsimatidis, a New York investor and grocery store magnate who attended the event at the Knickerbocker Club. “People are scared of Donald Trump, that’s why.”

Starting Friday in Las Vegas, Trusted Leadership, the chief super PAC supporting Cruz, will host a gathering intended to draw new donors to the group, until now financed by a handful of wealthy families. Not coincidentally, the event will be held at the Venetian, the casino hotel owned by the Republican megadonor Sheldon Adelson, perhaps the most sought-after contributor of all.

Kellyanne Conway, president of Trusted Leadership, summed up how prominent donors’ view of the Cruz-Trump fight had evolved. “It’s not just, ‘Would you rather be shot or poisoned?’” she said. “Now it’s, ‘This isn’t so bad.’”

One goal is to pry loose some of the large-scale money that went to candidates like Rubio and Bush earlier in the campaign. In recent months, as Cruz rose, some of the party’s wealthiest donors, such as the billionaire New York investor Paul Singer and the Ricketts family, chose to pour money into super PACs that are directly attacking Trump, rather than openly backing Cruz.

But the courtship is a delicate one. Some donors said that if Cruz was perhaps not their ideal choice for president — or even their third or fourth choice — he now seemed to be the only candidate with enough delegates to force a contested convention and deny Trump the nomination.

“It’s never really been a part of his brand, to be the unifying figure who could bring together the party, and it certainly was never part of his pitch,” said Chris DeRose, an Arizona lawyer who raised money for Rubio. “But the specter of Trump has done wonders to show us the downsides of losing this primary.”

For Cruz, help from establishment donors could dilute his outsider message and provide a new cudgel for Trump, who has denounced rivals for their dependence on contributions from the wealthy and powerful.

But as Cruz prepares for a long march to the Republican convention in July in Cleveland, he would not mind those donors’ help: His campaign, long powered by a loyal cadre of small contributors, spent far more money than it raised in January and February — burning through about $10 million more than it took in. (At his Wisconsin victory speech, Cruz said the campaign had raised more than $2 million Tuesday alone.)

Forty percent of his overall cash has come from small donors, many in Texas, and only about a fifth of his money for the primary has come from donors giving the maximum $2,700 contributions. At the end of February, according to the most recent financial disclosures, the campaign reported about $8 million cash on hand.

Cruz’s challenge is to broaden his reach in the world of midlevel Republican fundraisers — those who can raise tens or hundreds or thousands of dollars for his campaign — and among the elite group of billionaires who could write larger checks to the super PACs supporting him.

But doubts remain. Catsimatidis, one of about 30 people who attended the event at the Knickerbocker Club, pronounced Cruz “very, very smart,” but he said he wondered why “out of 100 people in the Senate, 99 don’t like him.”

Cruz is not always good at asking for help, sometimes giving the impression that he could as easily do without it. Even in private, donors said, he can be prone to sanctimony, disinclined to adjust his television-ready populism. Allies view Cruz’s uncompromising style as a virtue, but they concede it can make life difficult on the donor circuit.

Asked what was the biggest worry of prospective supporters, Doug Deason, a major Cruz donor in Dallas, did not hesitate.

“I think his personality, mostly,” Deason said, before defending him as likable to those who get to know him.

A wider embrace by donors has also been hampered in some quarters by genuine political disagreement between more middle-of-the-road potential donors and Cruz, a professed conservative purist on economic and social issues.

Andy Sabin, a former Bush supporter who runs a Long Island precious metals company, said that when a fundraiser from Cruz’s campaign reached out recently, he insisted on one condition.

“I told him, ‘For me to have any interest in Ted, I need him to accept that the earth has warmed, and that we can solve the problem and create plenty of jobs,’” Sabin recalled. Sabin said he was offered a spot on one of Cruz’s policy advisory committees, but that when he still asked that Cruz publicly voice a belief in climate change, he never heard back. Even a signal in the right direction would have been enough for him, Sabin said.

“All he had to do was say, we think it’s an issue for the general election, and maybe put Ted on the phone,” Sabin said, adding, “I felt I was being hustled for a donation.”

Cruz has reported raising only a few thousand dollars from registered lobbyists — a mainstay of fundraising for Rubio and Bush — suggesting that Cruz is still a tough sell among those he continues to deride as the “Washington cartel.”

Instead, Cruz and his surrogates are leaning heavily on his credentials as a supporter of Israel, now the most robust of any candidate. Many pro-Israel Republican donors had already backed him, and while in Washington recently to speak before the American Israel Public Affairs Committee, or AIPAC, Cruz attended a fundraiser tied to the event. Last month, he also gained the support of Fred Zeidman — a board member of the Republican Jewish Coalition who previously backed Sen. Lindsey Graham of South Carolina and Bush — and his son, Jay.

“There is no more staunch and vocal supporter of the state of Israel than Ted Cruz has been,” the elder Zeidman said. “And it is the primary reason I felt I had to support him.”

Elsewhere, support for Cruz has required fewer caveats. He is regarded warmly among Republicans in his home state, Texas, where he has deeper personal relations with a wider portion of the donor class. For longtime Cruz fundraisers there who seek to expand Cruz’s fundraising footprint in other corners of the country, it has been a heady few weeks. There are new calls to make and pitches to massage, given many audiences’ deep reservations.

“We weren’t their No. 1 draft pick,” Mica Mosbacher, a Cruz fundraiser based in Houston and New York, said of her discussions with new prospects. Mosbacher is among the supporters assigned to attest to Cruz’s charms.

“I call him a steady Eddie,” she said, before paraphrasing a Cruz answer from a past debate. “He might not be the most fun to have a drink at the bar with, but America needs a designated driver.”

Cruz has taken to making light of his détente with former critics and opponents, donors and otherwise. When Cruz appeared recently on “Jimmy Kimmel Live,” the late-night host took note of his patience in winning new friends.

“What you did is, you kind of held out until they found someone that they liked less than you,” Kimmel said.

“There you go,” Cruz replied. “Listen, it is a powerful strategy.”