"The other guy" took a cognitive test when people had serious concerns and he passed it with flying colors.
Why not have Biden do the same test?
A lot of times people think that dad/grandpa is still in a good shape because he can remember when birthdays are, drive his car or prepare food just fine.
But then the old timer has to draw a clock showing 12PM, remember 4 words or identify zoo animals and while those tests may seem childish, they often lead to shocking results.