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A top conservative group has started reaching out to major Republican donors seeking contributions for a multi-million dollar ad campaign aimed at taking down Donald Trump -- the latest sign of growing anxiety within GOP circles over the mogul's dominance in the 2016 race.

Officials with the Club for Growth -- a prominent anti-tax group that frequently targets Republicans it deems not conservative enough -- said Friday that the organization began reaching out to its network of donors in recent weeks to help fund an anti-Trump ad blitz. The organization's super PAC arm, Club for Growth Action, would run the ads, the group said.

The organization has long made clear that it is no fan of Trump and has feuded with the GOP candidate as he has risen in the polls.

“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.”

But the group’s pitch has been met with skepticism among some top GOP financiers, who believe that any effort to attack the real estate mogul could backfire, according to a person familiar with the conversations granted anonymity to speak frankly.

Trump has criticized the Club for Growth for attacking him after previously talking to him about donating money. In a Friday interview with The Post, he reiterated his criticism.

“This just shows you what politics has boiled down to in this country. It’s a disgrace," said Trump.

He continued: “I hear they’re trying to come after me and it’s all because I didn’t give them a million dollars. Had I given them the money, I would’ve been fine.”

“Who knows more about growth than I do?” asked Trump.

A day after the first Republican debate on Aug. 6 7, McIntosh sent an email 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."

While there is acute anxiety about Trump’s rise, there has not been an organized effort to try to undercut him. Some key party power centers are staying out of the fray, including the political network allied with billionaire brothers Charles and David Koch. The Koch operation is sticking to its plan to stay out of the primary fight and has no intention of launching an effort against Trump, according to people familiar with internal discussions who requested anonymity to speak frankly.

After Trump talked in Iowa earlier this summer about pressure he would apply of Ford Motor Company to move more of their overseas operations back to the U.S., McIntosh released a statement accusing Trump of threatening "to impose new taxes on U.S. car companies will hurt the American economy and cost more American jobs."

And while the group issued white papers on many other Republican candidates, it concluded in June that there was "no need to do a white paper on Donald Trump" because he "is not a serious Republican candidate," according to McIntosh.

Word of the move against Trump comes as former Florida governor Jeb Bush has ramped up his attacks against the real estate mogul, who has skyrocketed to the top of early state and national polls and has routinely gone after Bush and other Republican candidates.

The Club for Growth has already attacked longtime foe Mike Huckabee with an ad this year. In 2014, the group waged an expensive, high-profile effort to unseat Sen. Thad Cochran (R-Miss.) in the Republican primary, but fell short.

Philip Rucker contributed to this post