U.S. presidential hopeful Donald Trump speaks in New York on Sept. 3, 2015. (Lucas Jackson/Reuters)

A top conservative group is trying to coax wealthy Republican donors to help fund a multimillion-dollar ad campaign and other efforts against Donald Trump — the latest sign of growing anxiety within GOP circles over the businessman’s dominance in the 2016 race.

But some GOP financers are skeptical of the plan, fearing it will only fuel Trump’s outsider pitch. The lack of consensus illustrates how Trump, for the moment, is a problem without a clear solution in the eyes of party leaders worried that his controversial rhetoric and tactics are hurting the Republican brand.

Officials with the Club for Growth — a prominent anti-tax group that frequently targets Republicans it deems insufficiently conservative — said Friday that the organization began reaching out to its network of donors in recent weeks to help pay for an anti-Trump TV ad blitz. The organization’s super PAC, Club for Growth Action, would run the ads, the group said.

“What we’ve said to our members is that ‘Trump is a liability to the future of the nation,’ and we’ve asked them for support for Club for Growth Action to get that message out,” Club for Growth President David McIntosh said in a statement to The Washington Post. “We’re also doing research, like we do on candidates, into his economic policy positions. At this point, we haven’t taken anything off the table — be it TV ads or any other means — to expose Trump as not being an economic conservative and as actually being the worst kind of politician.”

Trump bashed the Club for Growth for its decision and said, as he has previously, that McIntosh asked him in June to donate $1 million to the group.

Business mogul and presidential candidate Donald Trump announced he signed the loyalty pledge that the Republican National Committee has demanded of its candidates during a news conference at Trump Tower in Manhattan on Sept. 3, 2015. (Reuters)

“They’re critical of me because I wouldn’t give them a million dollars,” Trump said in an interview with The Post. “They came to my office, the president of the Club for Growth came to my office; he asked for a million dollars. He asked for it in writing, just to show you how truly stupid he is. I said, ‘You must be kidding.’ I had no interest in doing it. . . . We told them no, and immediately thereafter, he came after Trump.”

Some top GOP donors pitched on the idea of attacking Trump think that any effort to go after the real estate developer and former celebrity TV host could backfire, said a person familiar with the conversations who spoke on the condition of anonymity to comment frankly.

Mary Beth Weiss — a longtime Club for Growth donor with her husband, money manager Richard T. Weiss — said Trump has tapped into the kind of outsider sentiment that the group has long sought to harness.

“Honestly, ‘The Donald’ is doing [the Club for Growth] a favor and sending a message to Washington,” Mary Beth Weiss said. “Ben Carson and Carly Fiorina and Trump are leading the field, and they’re all Washington outsiders.”

Weiss said she likes candidates Fiorina, a former chief executive of Hewlett-Packard; Wisconsin Gov. Scott Walker; and Sen. Marco Rubio (Fla.) but would support Trump if he were the nominee. “I would be happier writing a check to Donald Trump than [to former Florida governor Jeb] Bush, honestly,” she said.

Although there is acute anxiety in the GOP about Trump’s rise, no organized effort to undercut him has emerged. Among those staying out of the fray are donors allied with billionaire brothers Charles and David Koch, who are sticking with plans to avoid involvement in the primary process, according to people familiar with internal discussions and who also spoke on the condition of anonymity.

McIntosh said most of the feedback he has received on his plan has been about strategy.

Supporters wait for GOP presidential front-runner Donald Trump to speak Sept. 3, 2015, at a news conference in Manhattan after he signed a pledge to support the Republican nominee in the 2016 general election, ruling out a third-party bid. (Spencer Platt/Getty Images)

“The questions I’ve heard are more in the realm of how to expose Trump,” he said. “And that’s where we’re looking for the best approach.”

The effort comes as Bush, a frequent target of Trump’s taunts, has ramped up his attacks against the real estate mogul on the trail and in online advertising. Trump has shot to the top of early state and national polls over the past two months with his brash pitch to deport illegal immigrants and to “make America great again.”

The feud between Trump and the Club for Growth intensified in June when Trump highlighted a letter from McIntosh requesting a contribution after a meeting. Group officials say Trump’s team requested the meeting.

After the first Republican debate, on Aug. 6, McIntosh sent an e-mail to supporters encouraging them to give money online to help fund “a series of ads in key states aimed at educating Republican primary voters about Donald Trump’s real record.”

When Trump spoke in Iowa this summer about pressure he would apply on automaker Ford to move more of its overseas operations back to the United States, McIntosh pounced with a statement saying, “Trump’s threat to impose new taxes on U.S. car companies will hurt the American economy and cost more American jobs.”

The Club for Growth has issued research papers on a number of other Republican candidates, but McIntosh said the group concluded that there was “no need to do a white paper on Donald Trump” after he launched his campaign because he was “not a serious Republican candidate.”

Trump, who appears to relish fighting with critics of all kinds, pointed to his business career in attacking the Club for Growth’s signature mission.

“First of all, who’s more growth than me?” he asked. “I built an incredible company. Who’s more about growth than I am?”

One top donor to a rival campaign said there is no evidence that any Republican group or candidate has a clear plan to take Trump down.

“I don’t think anybody knows where this is going, exactly, or what to do,” said the donor, also speaking on the condition of anonymity to offer a candid perspective. “I’ve heard nobody say, ‘This is the answer.’ ”

Philip Rucker contributed to this report.