TFG is most definitely mentally impaired and absolutely morally unfit for the office of president.

The difference is Trump has a cult that creates pictures of him sporting a body like 1980's Arnold Schwarzenegger. They would vote for Trump if he was nothing more than a brain in a jar with a ticket-tape LED screen scrolling MAGA!

Biden has to deal with a coalition that is not dedicated to voting for him no matter what. He has to deal with his perceptions in the voting public. He doesn't have the floor that Trump does and he doesn't have the propaganda machine Trump does.

So in our two-choice system, the choice between a visibly aged and declining Biden and Trump, enough people might vote against Biden or just not vote at all, to put Trump back in the White House.