COLORADO SPRINGS, COLO. - In the final hours of their summer donor retreat at the tony Broadmoor resort, Charles and Liz Koch invited a select group of donors up to their suite for cocktails.

Doug Deason, a multimillionaire from Texas who supports Donald Trump for president, used the intimate occasion to approach Charles Koch for the second time in four days about meeting the Republican presidential nominee.

Deason urged Koch to reconsider his refusal to meet Trump, telling him, "You could help influence his policies; he really is an open book."

But Koch stuck firm; the Trump meeting wasn't going to happen.

"He said there's just really no purpose," Deason said.

Koch, the most powerful billionaire in conservative politics, is staying on the sidelines of this year's presidential race.

Unfortunately for Trump and the GOP, so are many of Koch's fellow travelers in the high-end donor community, particularly those in the tight orbit of Charles Koch and his brother David.

It's a big problem for Trump and the GOP, as it will give Democrat Hillary Clinton an advantage in the air and ground fight this fall. Expectations are that Clinton and her allies will spend at least half a billion more than Team Trump, an unprecedented cash deficit in the modern era.

It's also a significant frustration to Deason and other Trump supporters who can't quite understand why Charles Koch won't give Trump a personal hearing.

"They should meet. I mean, Charles is one of the most influential people. ... If you're an influential person you have an opportunity to meet with, you know, 50-50 chance he's going to be our next president of the United States, and you have an opportunity to influence his policy and let him know what your issues are, why wouldn't you take that?"

"I don't understand," added Deason, whose family has already written checks of more than $900,000 to Trump's campaign and the joint fundraising committee supporting him.

"It's illogical. [And Koch] is one of the most logical people I've ever met."

Koch's decision not to meet Trump is nothing personal.

He doesn't care how nice or charming Trump is.

Koch told Deason that he knew Trump socially. They'd played golf together, and David Koch moved in the same Manhattan social circles as Trump.

But Charles Koch bases all of his decisions - whether they're in business, politics or his personal life - on a set of "guiding principles" that underpin his free market philosophy. He is known to carry the checklist, which includes the words integrity, humility and respect, in his suit jacket pocket.

Koch's team, led by general counsel Mark Holden, has already met with the Trump campaign and decided there is not enough policy alignment for Koch to support Trump.

The conservative donor wants to get rid of ObamaCare, dramatically reduce the size and scope of government programs including social security, cut regulations, trim down the police state, end the public subsidization of green energy and scrap all government subsidies to corporations.

Koch sees no evidence that either Trump or Clinton would follow through on the Koch agenda. And the billionaire believes that a meeting between himself and Trump would only lead to unwanted media speculation and inevitable disappointment on both sides.

The Hill spent three days with the Koch network's 400-odd donors who attended the summer retreat. The Kochs invited several national reporters to attend the retreat on the condition that they not identify any donors without permission.

Over the course of attending seminars and talking to donors at the resort's bars and other informal spots, it became clear that many in Koch's network support his decision on Trump.

Many of those in attendance want to defeat Clinton, but they don't have enthusiasm for Trump.

"I don't think I've had a single person who's been enthusiastic about Donald Trump based on his position on the issues or his overall experience and qualifications," the influential North Carolina donor Art Pope said in an interview with The Hill at a resort bar on Sunday night.

Pope won't give a penny to Trump. And asked how he plans to vote in November, he said, "The election is still three months away, and I may not decide until I walk into the voting booth."

Chart Westcott, a Texas investor who gave $200,000 to Wisconsin Gov. Scott Walker's super-PAC during the primaries, said, "I may end up voting for him. ... But I'm not going to support him financially.

"He just doesn't align with my principles and my values."

Will McConathy, 34, is perhaps the youngest member of the Koch network.

While he appreciates Trump conceptually as a "much needed breath of fresh air," he said he's not giving the GOP nominee any money and can't say how he'll vote.

McConathy, the president of a Denver-based oil and gas company, also says he's not forgotten the promise Trump made during the primary season that he would do without donors.

"I'm not supporting Trump financially out of respect for his original declaration to be a self-funded presidential candidate that wouldn't give in to special interests, which of course insinuates that anyone like myself, who donates money for any political cause must, intrinsically, want something for it," McConathy said.

"I didn't ask Mr. Trump to make that promise, and wouldn't have ever recommended him doing so because it's not realistic ... but at some point Americans need to start believing, and believing in, its leaders again.

"It starts with the presidency, and we're tired of stepping in bullshit."

One well-known Koch donor, who asked to speak anonymously so he could be open in his thoughts, described the tough choice donors face with Trump.

"One of two things is going to happen with this election, in my view," the donor said.

"Either he's going to win, and politics is going to be so nasty, so disgusting, I'm not going to want to have anything to do with it, and to have been part of making that happen I wouldn't be proud of it."

"The flip side is he's going to lose, and history will not be kind to him or anyone who supported him. So those are to me the two outcomes," he added. "So why would I want to get involved in those two outcomes?"