John Kelly, the Trump White House’s longest-serving chief of staff, said that he believed that Donald Trump met the definition of a fascist.

Few top officials spent more time behind closed doors in the White House with President Donald J. Trump than John F. Kelly, the former Marine general who was his longest-serving chief of staff.

With Election Day looming, Mr. Kelly — deeply bothered by Mr. Trump’s recent comments about employing the military against his domestic opponents — agreed to three on-the-record, recorded discussions with a reporter for The New York Times about the former president, providing some of his most wide-ranging comments yet about Mr. Trump’s fitness and character.

Mr. Kelly was homeland security secretary under Mr. Trump before moving to the White House in July 2017. He worked to carry out Mr. Trump’s agenda for nearly a year and a half. It was a tumultuous period in which he drew internal criticism over his own performance and grew disenchanted and distressed by conduct on the part of the president that he considered at times to be inappropriate and reflecting no understanding of the Constitution.

In the interviews, Mr. Kelly expanded on his previously expressed concerns and stressed that voters, in his view, should consider fitness and character when selecting a president, even more than a candidate’s stances on the issues.

“In many cases, I would agree with some of his policies,” he said, stressing that as a former military officer he was not endorsing any candidate. “But again, it’s a very dangerous thing to have the wrong person elected to high office.

He said that, in his opinion, Mr. Trump met the definition of a fascist, would govern like a dictator if allowed, and had no understanding of the Constitution or the concept of rule of law.

He discussed and confirmed previous reports that Mr. Trump had made admiring statements about Hitler, had expressed contempt for disabled veterans and had characterized those who died on the battlefield for the United States as “losers” and “suckers” — comments first reported in 2020 by The Atlantic.

Steven Cheung, a spokesman for Mr. Trump’s campaign, assailed Mr. Kelly in a statement, calling Mr. Kelly’s accounts of his time in the White House “debunked stories” and saying Mr. Kelly had “beclowned” himself.

Here are excerpts from, and audio of, Mr. Kelly’s comments.

Kelly said that based on his experience, Trump met the definition of a “fascist.”

In response to a question about whether he thought Mr. Trump was a fascist, Mr. Kelly first read aloud a definition of fascism that he had found online.

“Well, looking at the definition of fascism: It’s a far-right authoritarian, ultranationalist political ideology and movement characterized by a dictatorial leader, centralized autocracy, militarism, forcible suppression of opposition, belief in a natural social hierarchy,” he said.

Mr. Kelly said that definition accurately described Mr. Trump.

“So certainly, in my experience, those are the kinds of things that he thinks would work better in terms of running America,” Mr. Kelly said.

He added: “Certainly the former president is in the far-right area, he’s certainly an authoritarian, admires people who are dictators — he has said that. So he certainly falls into the general definition of fascist, for sure.”

Kelly said Trump chafed at limitations on his power.

“He certainly prefers the dictator approach to government,” Mr. Kelly said.

Mr. Trump “never accepted the fact that he wasn’t the most powerful man in the world — and by power, I mean an ability to do anything he wanted, anytime he wanted,” Mr. Kelly said.

“I think he’d love to be just like he was in business — he could tell people to do things and they would do it, and not really bother too much about whether what the legalities were and whatnot,” he said.

He said he was deeply troubled by Trump’s recent comments about using the military against domestic opponents.

When Mr. Kelly left the White House in 2019, he decided he would speak out on the record only if Mr. Trump said something that he found deeply troubling or involved him and was wildly inaccurate.

Mr. Trump’s recent comments about using the military against what he called the “enemy within” were so dangerous, he said, that he felt he had to speak out.

“And I think this issue of using the military on — to go after — American citizens is one of those things I think is a very, very bad thing — even to say it for political purposes to get elected — I think it’s a very, very bad thing, let alone actually doing it,” Mr. Kelly said.

Mr. Kelly said that Mr. Trump was repeatedly told dating back to his first year in office why he should not use the U.S. military against Americans and the limits on his authority to do so. Mr. Trump nevertheless continued while in office to push the issue and claim that he did have the authority to take such actions, Mr. Kelly said.

“Originally, conversation would be: Mr. President, that’s outside your authority, or you know that’s a routine use, you really don’t want to do that inside the United States,” he said. “But now that he’s talking about it as ‘I’m gonna do it’ is, again, it’s disturbing.”

He said he believed Trump stood alone in his lack of understanding of history and the Constitution.

Mr. Kelly said Mr. Trump lacked a fundamental understanding of basic American values and what being president is about.

“He’s certainly the only president that has all but rejected what America is all about, and what makes America America, in terms of our Constitution, in terms of our values, the way we look at everything, to include family and government — he’s certainly the only president that I know of, certainly in my lifetime, that was like that,” Mr. Kelly said.

“He just doesn’t understand the values — he pretends, he talks, he knows more about America than anybody, but he doesn’t.”

He said Trump wanted personal loyalty to outweigh loyalty to the Constitution.

Mr. Kelly said that in the first few days of working for Mr. Trump as his chief of staff in the summer of 2017, he had to explain to the president that top government officials like himself had taken an oath to the Constitution and would place that oath over personal loyalty.

Mr. Kelly said Mr. Trump pressed him about that pledge and seemed to have no appreciation that top aides were supposed to put their pledge to the Constitution — and, by extension, the rule of law — above all else.