Columnist Charles Krauthammer argued that the GOP is “being led by a non-conservative populist” and that from what he’s seen so far, “I don’t think I’d be capable of voting for Donald Trump” on Tuesday’s “O’Reilly Factor” on the Fox News Channel.

Krauthammer said [relevant remarks begin around 3:30] “[W]hat we are just witnessing happening tonight, is one the major American parties changing its political ideology radically. It was, until now, for the last 50 years, going all the way back, perhaps to Eisenhower, the conservative party in the country. As of tonight, it’s being led by a non-conservative populist. Populism is a perfectly legitimate political philosophy, but it’s not conservatism.”

When asked if he would vote for Trump, Krauthammer answered, “I have not decided what I’m going to do except for this, that I’m going, as I have up until now, to try to state what I see as the future of the party. And the question is, are we going to have a conservative program before us or not? I don’t know, but we’ll see.” Krauthammer added, [F]rom what I’ve seen up until now, heard from Trump, and watched him, I don’t think I’d be capable of voting for Donald Trump. Question is, what do I do? I don’t know yet.”

He was later asked, “[I]f he presents himself as a populist with conservative platform, why couldn’t you vote for him?” Krauthammer responded, “As of now, I don’t believe that he is. And I don’t, — I think he has actually told us what he believes, and he clearly is not a conservative.”

After O’Reilly objected, “But his platform will be conservative. What he presents will be conservative.” Krauthammer countered, “You and I know that a platform doesn’t mean a damn thing. what has he been saying, what has he been advocating? that’s what counts. And there’s a second issue, is his fitness for office. It’s a matter of temperament, and up until now he’s not impressed me with his temperament. … I think you have to ask yourself, do I want a person of that temperament to control the nuclear codes, and as of now, I’d have to say no.”

O’Reilly then stated, “I know Trump, and I know that he deals — he says things out of emotion. For example, today, with the Ted Cruz father business.” O’Reilly further added that while Trump’s claim, which is based on a National Enquirer story, is “bizarre” and doesn’t do the GOP any good, Trump “gets emotional,” and “I believe he puts that out there just to create mayhem, and creating mayhem has won the election for him. Has it not?”

Krauthammer responded that this was saying that the end justifies the means. O’Reilly stated that he was just saying how Trump views it, and that “a lot of this is theater, because the odds of him winning the nomination when he began in June were a million to one, and he won it by creating mayhem, and it was a brilliant strategy. It worked for him.”

Krauthammer responded by asking whether “Twilight Zone” “conspiracy theories” pushed by Trump said something about his temperament? O’Reilly answered, “It tells me that he wants to win, and his playbook is much different than the traditional playbook.”

Krauthammer concluded, “[P]laying with absurd and kooky conspiracy theories is way beyond being unconventional, it is disturbing. And that’s what you’ve got to ask yourself, do you want somebody who does that, in control of the nuclear codes?”

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