Texas Republican Rep. Ronny Jackson, who served as Donald Trump‘s White House physician, has sent President Joe Biden a letter urging him to take a cognitive test to prove he is ‘mentally fit to be commander in chief’.

Jackson has been circulating the letter with House colleagues and has been able to get the signatures of 13 GOP  lawmakers.

The letter cites the president’s ‘mental decline and forgetfulness’, notes several of his ‘gaffes’, and urges the White House to publish the test results immediately.

It goes on to list examples of moments of the president’s apparent confusion – forgetting the name of the Defense Secretary, muddling Air Force One with Air Force Two, and apparently forgetting the words to the first line of the Declaration of Independence.

‘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,’ he said in an interview with The Hill.