Donald Trump sat down for three hours on Friday with Joe Rogan, telling the US’s most-listened-to podcaster that the biggest mistake he made during his presidency was hiring “disloyal people”.

Those comments – which also described “neocons”, or neoconservatives who generally aim to promote democracy, as “bad people” – came days after the Trump White House’s former chief of staff John Kelly said the Republican nominee in the 5 November election met the definition of a fascist. Kelly also said Trump had no understanding of the US constitution and made admiring statements about generals commanded by Adolf Hitler, whose regime systematically murdered 6 million Jews as part of the Holocaust during the second world war.

At a rally on Friday that he held apart from his conversation with Rogan, Trump described Kelly as a “total whack job”.

Trump used his interview with Rogan on Friday to repeat his claim that his defeat in the 2020 presidential election against Joe Biden was a “rigged” outcome. But Trump changed the subject when Rogan asked him if he was ever going to release evidence proving the election was “stolen”.

Trump also said: “If I win, this will be my last election.” That was a true statement because the constitution would bar him from serving beyond a second term in the White House. Yet it seemed to contradict an earlier campaign promise that he would not run for the Oval Office again if he lost to Kamala Harris in the 5 November election.

In another part of the show, the former president tried to address the age-related questions which forced Biden, 81, to drop out of seeking re-election – and which have since been redirected at Trump, 78.

Trump tried to convince Rogan that Biden was in cognitive decline because of brain surgery.

“It’s not his age,” Trump said. “Those are not good operations.”

Rogan alluded to how brain surgeries saved Biden’s life after he endured two aneurysms in the 1980s, when he was a US senator for Delaware before serving as vice-president to Barack Obama and then winning the presidency himself.

The reach of Rogan’s show, estimated at 14 million listeners on Spotify with an 80% male audience split between Democrats, Republicans and independents, has developed a reputation as a useful platform for seekers of political office.

But the interview, which was recorded in Rogan’s Austin, Texas, studio, delayed Trump’s arrival at an outdoor rally in Traverse City, Michigan, in cold 50F (10C) temperatures. The Associated Press reported that some rallygoers were already leaving by the time Trump arrived.

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The rally was expected to begin at 7.30pm, but by that time Trump was only then leaving Texas. The ex-president recorded a video from his plane urging his supporters to stay, seeming to suggest that many rallygoers would not have work the next day because it was Friday and promising: “We’re going to have a good time tonight.”

“I am so sorry,” Trump said when he arrived. “We got so tied up, and I figured you wouldn’t mind too much because we’re trying to win.”

Meanwhile, Harris was in Houston, Texas, with superstar singer Beyoncé to drive her message opposing the conservative state’s abortion ban as she attempts to become the first woman ever elected as US president.

“We are at the precipice of an incredible shift,” the Houston-raised singer told the crowd of 30,000 people. “Our moment is right now. It’s time for America to sing a new song.”

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