Rep. Ronny Jackson (R-Texas), who stirred controversy as former President Trump’s White House physician, said Thursday he is circulating a letter among House GOP colleagues that calls on President Biden to take a cognitive test to prove he is mentally fit to be commander in chief.

Jackson began collecting signatures for his letter this week during GOP meetings and House votes. It will be sent to Biden and his team in the next day or two, he said.

“Just everything that has been going on for the last year and a half … [Biden] doesn’t know what’s going on, where he’s at. He’s very confused all the time,” Jackson said in a brief interview with The Hill.