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President Trump suggested on Fox News' "Hannity" Thursday night that presumptive Democratic presidential nominee Joe Biden had been "brainwashed" by the party's far left.

"He's been taken over by the radical left. He has no clue what they're doing and what they're getting him into," Trump told host Sean Hannity. "And you look at the deal they made with Bernie Sanders now and the group, it's all crazy, radical left stuff. And Joe's never going to be able to fight it, even if he disagreed with it, which I actually don't think he does.

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"I think they brainwashed him," the president added. "They brainwashed him. He doesn't know where he is. He doesn't know what he's doing. And our country will suffer. Our stock markets will crash. Bad things will happen.

"They will defund the police. They will abolish the police. It will be, maybe [there will be] a backlash or maybe it'll just go to hell like Venezuela."

Later in the interview, Hannity asked Trump if Biden was trying to "back out" of scheduled debates this fall, which prompted an odd exchange as to whether or not Biden said he regularly underwent "cognitive" tests or COVID-19 tests.

"He meant the COVID tests," Trump said. "He didn't mean 'cognitive'. He meant 'COVID'."

Hannity responded that the former vice president had said at a press conference last week that his cognitive ability was "constantly tested."

"He didn't mean that because you don't have those tests that often," Trump insisted before challenging Biden to take the same cognitive test he underwent at Walter Reed Medical Center in 2018. "He didn't mean that because he hasn't taken any cognitive test because he couldn't pass one."

Trump also mocked Biden for his appearance while wearing a "massive" mask, saying it makes the Democratic nomiee "feel good."

"I expect to be wearing a mask when I go into Walter Reed. You're in a hospital setting. I think it's a very appropriate thing," Trump acknowledged. "I have no problem with a mask. I don't think you need one when you're tested all the time. Everybody around you is tested."

The president once again defended his administration's handling of the coronavirus pandemic, telling Hannity that White House coronavirus task force member Dr. Anthony Fauci is a "nice man" before claiming that he had made "a lot of mistakes." He also criticized the media for focusing on the rise in cases and ignoring the decline in the death rate.

"They don't talk about death because deaths are way down," Trump said.

The president also flirted with the idea of pardoning key figures in the Russia investigation, including longtime ally Roger Stone, former campaign chairman Paul Manafort and former National Security Adviser Michael Flynn.

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"President Obama and Joe Biden spied on my campaign," Trump insisted. "They knew everything that was going on. They were in the rooms when everyone was talking about it. These people all work for them. I know how the White House works. I guess I can say now better than anybody. And they knew everything that was going on."

Trump declined to commit to any pardons Thursday night, but told Hannity, ""I am always thinking, I am always thinking."

Fox News' Paul Steinhauser and Allie Raffa contributed to this report.