Libertarian and conservative donors who attended the annual Koch network summit over the weekend discussed the need to defend the GOP majority in the Senate as a backstop in case a Democrat defeats President Donald Trump in November.

People at the meeting in Palm Springs, California, didn't just fret about progressive candidates Sens. Bernie Sanders and Elizabeth Warren winning — they were also concerned about the moderate former Vice President Joe Biden, according to attendees who declined to be named since the conversations were deemed private.

These people said that all three candidates have proposed policies that would fly in the face of the free-market philosophy shared by much of the network, which is partially funded by billionaire Charles Koch.

"Sanders and Warren provided the most fright," said one of the attendees.

Both Sanders and Warren have called for enhanced corporate regulation, large tax hikes on the rich and businesses, and a universal "Medicare for All" health insurance plan. And while Biden has rejected Medicare for All, he has also called for raising taxes. Biden maintains a lead in national polls, according to a Real Clear Politics average, ahead of Sanders and Warren.

The network, according to people familiar with the matter, believes these policies are a form of government overreach. Brian Hooks, the chairman and CEO of Stand Together, told attendees that he sees ideas borne out of socialism and nationalism as a threat to America, pointing to what was described as trade protectionism, class warfare, the demonization of immigrants, and nationalization of industries, according to a person familiar with the matter.

A Stand Together spokesman declined to comment on the conversations with donors.

The network has already said it would not be getting involved with the 2020 presidential election. Rather, it is focused on implementing policy goals, rather than getting involved in partisan politics.

In an introductory video that played at the summit, Charles Koch himself said the group is seeking to unite people.

"Both parties have fallen into tribal warfare," he said. "We are offering a different approach: uniting people, regardless of political party, to advance policies that empower people."