President Trump said Joe Biden is his preferred challenger because he appears weaker than other Democratic hopefuls.

“I’d rather run against, I think, Biden than anybody. I think he’s the weakest mentally and I like running against people that are weak mentally. I think Joe is the weakest up here,” Trump said pointing to his head. “The other ones have much more energy.”

Trump also claimed Biden’s campaign could be “in trouble.” Biden has skipped two big Democratic gatherings in the last two weeks, though he has been consistently leading in the polls.

The president and Biden are both holding events in Iowa on Tuesday. Biden is set to give a speech calling Trump an “existential threat” to decency, America’s standing in the world, and democracy.

“When a man has to mention my name 76 times in his speech, that means he’s in trouble. Now, I have to tell you, he’s a different guy. He looks different than he used to. He acts different then he used to. He’s even slower than he used to be,” Trump told reporters before heading to the Midwest.

“I heard Biden, who’s a loser, I mean look, Joe never got more than 1% … It looks like he’s failing, it looks like his friends from the Left are going to overtake him very soon,” he said.