(Bloomberg) —For all his prowess at appealing to Republican voters, Donald Trump has struggled mightily to win over rich Republican donors. After savaging major party funders as corrupt insiders during the primaries, Trump is finding them reluctant to open their wallets. With Trump’s campaign reeling and nearly broke — new filings show it has less than $1.3 million cash on hand— outside allies are stepping in.

Robert Mercer, the GOP mega-donor and co-founder of Renaissance Technologies hedge fund who once backed Texas Senator Ted Cruz, is launching a super-PAC with a novel twist to get establishment-minded donors off the sidelines. The new project will informally be dubbed the “Defeat Crooked Hillary PAC” and, despite its Trumpian name, will focus solely on attacking Clinton, not boosting Trump. The idea is that conservative donors reluctant to support Trump can still donate in good conscience to a super-PAC that only attacks Clinton. “It’s a way to participate without [directly] supporting Trump,” says a source involved in the super-PAC’s creation.

Mercer’s new anti-Hillary vehicle is actually a refurbished version of Keep the Promise PAC, a pro-Cruz super-PAC that Mercer and his daughter Rebekah poured $13.5 million into during the primaries. Kellyanne Conway, the Republican pollster who is president of Keep the Promise PAC, may leave to join the Trump campaign.

David Bossie, president of the conservative advocacy group Citizens United, will take over as the head of Defeat Crooked Hillary. “This is an opportunity to really refocus the presidential debate around Hillary Clinton and her character, and the whole culture of corruption that’s surrounded the Clintons for decades,” says Bossie.

Conway said that she recruited Bossie for his role at the super-PAC, but hasn’t decided what she’ll be doing next.

“Very few people have studied Hillary Clinton longer or stronger than Dave Bossie, and I support him in this role as I decide where I can be most helpful in defeating Hillary Clinton,” she said.

Bossie says that the name Defeat Crooked Hillary PAC won’t actually appear in Federal Election Commission filings. “Technically, the name of the super-PAC is going to be ‘Make America Number One,’” Bossie says. “If we call it ‘Defeat Crooked Hillary,’ it’s an FEC violation. You have to do these things because of the way federal election law works.”

Bossie would know. It was his 2007 anti-Clinton film “Hillary: The Movie” that was the basis of the 2010 Supreme Court case, Citizens United vs. Federal Election Commission. The court ruled 5-4 in Bossie’s favor, opening the floodgates for more private money in politics.

However, many of the Republican donors who took advantage of the court’s ruling have refused to support Trump. The Mercers hope that Defeat Crooked Hillary will open a pathway for them to do so, at least indirectly.

“Some donors don’t want to associate with something overtly pro-Trump,” says Bossie. “This gives people an opportunity to aggressively get involved at whatever level they might want but have it solely focused on being a Hillary Clinton effort.”

Together with his wife Diana, Robert Mercer, 69, is the biggest-spending political donor in the 2016 election cycle, according to a tally by the Center for Responsive Politics. Mercer has a penchant for investing in anti-establishment candidates and quirky causes, including an annual fringe-science convention and a conference for proponents of the gold standard. He spent the first part of his career as a programmer at IBM, where he pioneered the use of computers to process human language. He later joined Renaissance Technologies, a Long Island hedge fund that uses advanced mathematics to spot patterns in financial markets. He’s now the co-chief executive officer of the firm.

Rebekah Mercer, his daughter, has devoted considerably resources to stopping Clinton. Mercer was a funder and board member of the Government Accountability Institute, a nonprofit group that produced the bestselling 2015 book, Clinton Cash: The Untold Story of How and Why Foreign Governments and Businesses Helped Make Bill and Hillary Rich; she also served as a co-executive producer of the “Clinton Cash” movie, which debuted in Cannes, France in May.

According to three sources involved in the Defeat Crooked Hillary effort, Trump’s daughter Ivanka and her husband Jared Kushner approached the Mercers after Cruz dropped out of the Republican race on May 3rd to say they would be supportive of any effort to help Trump. The Mercers agreed. “This will be one of the super-PACs that Trump will make clear he supports,” says a source involved in the effort. On Wednesday, Trump will give a speech at Trump Soho which a Trump campaign source says will be focused on attacking Clinton; at the same time, Defeat Crooked Hillary will release its first ad, which Bossie says will begin airing in battleground states next week.

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Although Keep the Promise PAC raised $14.2 million this cycle, disclosure filings show that it had only $1.3 million cash on hand as of May 31st. Bossie says the Mercers and other donors will recapitalize the super-PAC with a “substantial” budget. He and other sources declined to give a dollar figure. “We are in conversations with many top donors across the country who have indicated that they have been waiting for a super-Pac that is devoted to being anti-Hillary,” he says.

It remains to be seen whether major Republican donors who declined to support Trump directly will be willing to do so by funding attacks on her Democratic rival. One source involved in the effort said the aim was to attract establishment-minded GOP donors such as Paul Singer, who runs the hedge fund Elliott Management. A representative for Singer declined to comment.

With Trump signaling his eagerness to attack Clinton, Bossie believes a well-funded super-PAC could amplify those charges and further damage the presumptive Democratic nominee, whose lofty unfavorability rating is exceeded only by Trump’s. “It reinforces the dishonesty and distrust that we see in her polling numbers,” says Bossie.