In the first debate vs Mondale it was said he looked old and confused and rambling. The rnc held a press conference days later to deny questions about his mental decline and he dropped 5+ points in the polls.
As someone who protested outside a Reagan rally in 1984 and was pelted with sandwiches (!) kindly allow me to inform the assembled worthies I haven't forgotten The Gipper napped in cabinet meetings.
Reagan had Alzheimer’s. Maybe Biden can also quip that he won’t exploit for political purposes Trump’s youth and inexperience. I don’t think it will work for him like it did for Reagan.