COLORADO SPRINGS — Thirteen years after billionaire industrialist Charles Koch gathered a small group of his fellow libertarian donors in a Chicago hotel to discuss how to promote their economic theories, the network he launched is one of the country’s most potent political forces, with 1,600 staffers across 38 states.

But Koch’s refusal to harness his singular operation in support of the Republican presidential nominee, Donald Trump, has put him at odds with some of his wealthiest peers — and forced the network to defend its relevance at a time of its greatest reach.

That tension rippled behind the scenes this weekend as about 400 donors met in Colorado Springs at a luxury resort encircling a man-made lake, where white swans paddled in the shadow of the Rocky Mountains. Between panels extolling free speech and conservative state-policy victories, Koch and his top deputies heard out donors worried about the network’s decision to sit on the sidelines.

“I told him that it was very important that Hillary Clinton not get elected,” said Minnesota media mogul Stanley Hubbard, who said his biggest concern is how she would reshape the Supreme Court.

Koch’s decision not to embrace Trump threatens to alienate some heavyweight network backers who have rallied to the nominee’s side in recent months — mega-donors such as Wisconsin roofing billionaire Diane Hendricks, Oklahoma oilman Harold Hamm and New York hedge-fund magnate Robert Mercer, none of whom attended this weekend’s conclave.

“A lot of donors are saying, ‘Why are we spending money on Senate candidates and not trying to beat Hillary?’ ” said one well-connected Republican familiar with the views of major-party financiers, who requested anonymity to describe private conversations.

Network officials sought to defuse some of the frustration by announcing that Koch-backed groups would feature the Democratic presidential nominee, Clinton, in Senate campaign ads, tying her policy stances to those of Democratic contenders in battlegrounds states such as Ohio.

And on Sunday, Koch made his most forceful rejection yet of the possibility that he would personally support Clinton in this year’s White House race, calling such an idea “blood libel.” But he reiterated that he would not get behind Trump, whose rhetoric about immigrants and Muslims has appalled the 80-year-old chief executive.

[Charles Koch won’t back Trump but calls the idea that he would support Clinton ‘blood libel’]

Later, in a closed session for donors in one of the Broadmoor resort’s rose-colored villas, Koch and senior network officials detailed their reasons for staying out of the presidential contest. The 700 major contributors who support the organization were divided over the GOP nominee, they told attendees, and they think the network will have a greater influence by focusing on Senate races instead of splitting its resources.

But their main argument came down to credibility: If the network lent its weight to bolster Trump, who does not share the organization’s positions on core issues such as free trade and limited government, how could it deny similar support to any other Republican in the future?

The reaction was supportive, according to multiple people in the room. “I think they made a very good case,” Hubbard said.

Read more at washingtonpost.com.