Regardless of how much Trump has declined mentally he was never all that sharp. I recall mocking him in blog posts long before his 2016 run when he made claims such as that climate change does not exist because it is cold outside.
@rchusid I agree, he hasnt really declined mentally much at all, thats just the democrats trying to deflect from Bidens senility.
That said I fully agree that Trump is and always has been a raging lunatic and moron with questionable mental faculties. It has less to do with age and more to do with a life long laziness of the mind.