Charles Koch has criticized the tone of the GOP presidential primary campaign. (Bo Rader/the Wichita Eagle via AP)

Conservative political activist Charles Koch suggested in an interview with ABC News on Sunday that Democrat Hillary Clinton would be a better president than the Republican contenders, although he stopped short of saying he would support the former secretary of state if she ends up representing her party in a general election.

The billionaire, who with brother David has been active in Republican Party politics, criticized the tone of the GOP presidential primary campaign, citing it as the reason the brothers have not contributed to any campaigns, including efforts to derail Republican front-runner Donald Trump.

In the interview with chief White House correspondent Jonathan Karl, which aired on ABC’s “This Week With George Stephanopoulos,” Charles Koch said Bill Clinton had done a better job than George W. Bush in controlling government growth while president.

“So is it possible another Clinton could be better than another Republican?” Karl asked.

“It’s possible,” Koch responded.

“You couldn’t see yourself supporting Hillary Clinton, could you?” Karl pressed.

Koch responded: “Well, I — that — her — we would have to believe her actions would be quite different than her rhetoric, let me put it that way. But on some of the Republican candidates we would — before we could support them — we’d have to believe their actions will be quite different than the rhetoric we’ve heard so far.”

Charles and David Koch are hated by Democrats and loved by Republicans. But regardless of which party you support, there’s almost no question that the Koch Brothers have made money off of you. (Jeff Simon/The Washington Post)

Koch said he has not and probably will not back any Republican in the waning weeks of the primary campaign because of the divisive rhetoric.

“We said, ‘Here are the issues: You’ve got to be like Ronald Reagan and compete on making the country better rather than tearing down your opponents,’” he said. “And right off the bat, they didn’t do it. More of these personal attacks and pitting one person against the other, that’s the message you’re sending the country. That’s the way you should — you’re role models, and you’re terrible role models.”

He slammed Trump’s call for a ban on Muslims entering the country as “antithetical to our approach, but what was worse was this ‘We’ll have them all register’ [notion]. That’s reminiscent of Nazi Germany. I mean that’s monstrous, as I said at the time.” Koch was referring to comments Trump made, then backed away from, in the fall suggesting that he was open to the idea of a database to track Muslims in the United States.

He also had harsh criticism for Sen. Ted Cruz’s threat to “carpet-bomb” the Islamic State militant group. “Well, that’s gotta be hyperbole, but I mean that a candidate, whether they believe it or not, would think that appeals to the American people — this is frightening.”

Koch said he and his brother, who in the past have spent millions backing conservative Republican candidates and causes, have stayed out of the primary fight, including efforts to stop Trump from getting the party’s nomination.

“We read — I read, oh, we’ve given millions to this one, millions to that one, and millions to oppose Trump. We’ve done none of that. We haven’t put a penny in any of these campaigns, pro or con,” he  said.

He suggested that he was moving away from that kind of heavy spending in national politics because the return on his investments “has been disappointing.”

Asked whether he would sit out the presidential election, Koch said: “Well, we’ll see. I mean, when we get a nominee, then we’ll explore that. And we don’t want arm-waving. We want to know specifics.”