“Daily Show” correspondent Michael Kosta said Donald Trump and his Republican allies are worried he is going to lose this week’s debate with President Joe Biden.

Since they’ve also spent years attacking Biden’s cognition, they’re already making excuses by claiming the president is taking brain-enhancing drugs.

Kosta, who is hosting the show for part of this week, called that “such a stupid conspiracy theory.”

“If Biden’s body could handle even half of what they’re saying, he’s the strongest man alive,” he said. “He’ll win the presidency and the Kentucky Derby.”

Kosta said Trump, the presumptive Republican nominee for president, isn’t one to talk in any case. In the same speech on Saturday in which he claimed Biden is suffering from brain problems, Trump struggled with a basic word.

“My stupid people, when I wanted to refute it, they said, ‘Sir, don’t dignify it with a ...’” and here, the former president couldn’t quite find the word he was looking for. “Re-futtal. Refute-al? Or a re-futtal? What the hell word would that be? Re-futtal? They’ll say he didn’t know, re-futtal or refute-al, but they don’t know either.”

“It’s neither!” Kosta said. “It’s neither of those words! What do you mean, ‘They don’t know’? No, I don’t know what fake word you’re trying to say.”

Kosta took a peek inside the former president’s head.

“This dude’s entire brain is just squiggly red spellcheck lines,” he said. “And then his mouth always tries to re-futtal every thought he has.”

But he said that’s also a key difference between Biden and Trump.

“When they make a mistake, Biden will correct himself whereas Trump will deflect and call everyone else an idiot,” Kosta said. “Which, to be honest, is more relatable.”

See more in his Monday night monologue: