As Donald Trump inches closer to becoming the U.S. Republican nominee, many of the party's big donors fear they will tarnish their reputations should they contribute to a candidate who has insulted women, Hispanics and Muslims.

Some flatly reject the notion of ever funding his campaign.

In interviews with Reuters, 22 members of the Republican money class spoke of the “anguish,” “struggle,” and “Catch-22” they now find themselves in, especially in light of the violence at Trump rallies and the candidate’s refusal to denounce it.

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Two additional high-profile Republican donors, Gaylord Hughey of Texas, who backed Jeb Bush's Super PAC, and Ronald Firman of Florida, who poured more than $2 million into a conservative Super PAC, said they were still undecided and hoped Trump would tone down his inflammatory rhetoric and urge his supporters to eschew violence.

Trump won at least three states on Tuesday but his loss in Ohio means the Republican nominating convention in July may be contested if he falls short of winning a majority of delegates in the state-by-state contests.

Republican donors are a testing ground for Trump, who is under pressure to soften his tone to win independent voters. Even an unorthodox campaign like his is expected to need some money for television ads and staff should he reach the general election. The billionaire real estate developer may find it difficult to fund this with his own wealth.

Throughout the 2016 election, many establishment donors have viewed themselves as dedicated soldiers, willing to go to any lengths to prevent either Hillary Clinton, the Democratic front-runner, or her rival Bernie Sanders from winning the Nov. 8 election to succeed President Barack Obama.

But some Republicans said they worried that becoming a Trump donor could taint legacies, family names and personal brands. Many said they disagreed with his protectionist trade policies, his calls for the building of a wall on the Mexican border and his proposal for a temporary ban on Muslims entering the United States.

Energy magnate and mega donor Dan Eberhart said he was concerned about Trump’s lack of specificity on foreign policy and some of his rhetoric.

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“We won’t be donating to Trump, and I don’t know any of our donor peers that would donate,” said Eberhart, who was a supporter of Wisconsin Governor Scott Walker in the race. “If he’s the nominee, we will support him in spirit but not in cash. I mean, in some ways it’s refreshing to have a candidate who is not completely scripted but at the same time he lacks the decorum and stage presence and gravitas to deal with foreign leaders on the world stage.”

Added Denver technology executive Chris Wright, “It’s an anguishing position to be in, but we just couldn’t support him if he were the nominee. We’re appalled. He’s anathema to the free society and civil society in which we believe.”

In the run-up to the convention Trump has vowed to self-fund his campaign. He has pledged to do away with the pay-to-play, transactional politics that have long dominated Washington.

But were he to become the party's nominee, the growing consensus among campaign veterans is that a general election would cost hundreds of millions of dollars, a total that Trump may well be less able to self-fund.

Trump will likely face a barrage of attack ads and negative mailings funded by Super PACs, labor unions and the campaign of his Democratic opponent. Answering the charges on the airwaves would require more than just giving interviews and prove costly.

In a debate last week Trump said he had yet to decide whether to seek donations in a general election campaign.

To date, Trump’s controversial comments and his celebrity status – he is a former reality TV show host – have made him a regular presence on network television, allowing him to avoid spending as much as his rivals on paid television advertising.

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He has run a threadbare campaign from his plane and employs a tiny staff with no strategists, consultants or pollsters. Trump spent a mere $3.20 per vote versus now-dethroned rivals Bush and Marco Rubio, who spent $551.70 and $30.40, respectively.

Trump could always try to keep up his unconventional low-budget tactics. But Republican challenger Mitt Romney’s failure to respond to President Barack Obama’s television attack ads in 2012 offer a cautionary tale about not responding when an opponent goes on the offensive.

“What you [will] see is a lot of people concede if Trump is our nominee that we’ve lost the White House, let's protect the majority in the Senate and the majority in the House,” said David McIntosh, president of the Club For Growth, a conservative organization that has spent millions of dollars on ads aiming to defeat Trump in the primaries.