Trump expects Biden to be a 'worthy debater' after spending months attacking his mental fitness

Former President Donald Trump is raising his debate expectations for President Joe Biden a week ahead of the two men facing off, and after spending months describing him as a weak, mentally unfit leader.

"I assume he's gonna be somebody that will be a worthy debater. ... I don't want to underestimate him," Trump said during an episode of the "All In" podcast, hosted by Silicon Valley entrepreneurs Chamath Palihapitiya, Jason Calacanis, David Sacks and David Friedberg, and released on Thursday.

Pointing to Biden's vice-presidential debate performance against former House Speaker Paul Ryan, who ran as the VP choice of Sen. Mitt Romney in his 2012 presidential campaign, Trump, in a rare moment, praised Biden.

"All I can say is this, I watched him with Paul Ryan, and he destroyed Paul Ryan. Paul Ryan with the water, he was chugging water left and right … and he beat Paul Ryan. So, I'm not underestimating him. I'm not underestimating him. It is what it is."

Trump’s comments are a departure from his previous rhetoric and come as his campaign advisers have warned that Biden may overperform on Thursday because expectations have been set low for him, though Trump himself has contributed to those conversations.

"Crooked Joe Biden is the WORST debater I have ever faced - He can't put two sentences together!" Trump posted on his social media platform when he accepted Biden's debate proposal.

"I would strongly recommend more than two debates and, for excitement purposes, a very large venue, although Biden is supposedly afraid of crowds - That's only because he doesn't get them."

After Trump and Biden agreed to face off twice, Trump called for Biden to be drug tested ahead of the debates, claiming that if he performed well, it would be because of some kind of performance enhancement.

"I'm gonna demand a drug test, by the way. I am. No, I really am," Trump said at a campaign event in Michigan last month.

"I don't want him coming in like the State of the Union. He was high as a kite. They said 'Is that Joe up there in that beautiful room?' And by the end of the evening, he's like, where? He was exhausted, right?" Trump continued, making unfounded claims that Biden was on drugs during his State of the Union address.

Trump also previously floated the idea that Biden would be replaced as the Democratic nominee if he performed poorly at the debate, quipping that he would "lose the debate on purpose," to ensure Biden stays in the race.

"Maybe I'm better off losing the debate, I'll make sure he stays. I'll lose the debate on purpose, maybe I'll do something like that," Trump said during an interview with Real America's Voices the day he visited with Congressional Republicans.

However, now as the debate inches closer, Trump has started to plant seeds of doubt with his supporters about potential ways Biden could exceed expectations, complaining about the logistics of next Thursday's first debate and potential media coverage.

At his most recent rally in Racine, Wisconsin, Trump criticized debate moderators Dana Bash and Jake Tapper, arguing they won't be fair to him, and labeled their network, CNN, which is hosting the debate, as "fake news."

"I'll probably be negotiating with three people, but that's OK. I've done that before where I'll be debating three people instead of one-half of a person," Trump previously said, continuing to attack Biden's mental fitness.

He has also claimed that Biden's metric of success won't be based on performance but on mere completion.

"If he's standing, they'll say it was a brilliant performance," Trump told an NRA Convention crowd last month in Dallas.

Ahead of Thursday, both candidates have taken different approaches to preparation. While Biden is hunkering down at Camp David, participating in mock debates and refining his message with advisers, Trump has been holding policy meetings with his vice presidential candidates and former administration officials.

The second debate, hosted by ABC, airs Sept. 10.