It's time for the Donald to get a brain scan. At age 70, it should be part of the routine medical checkup for a person his age.

And if he wriggles himself out of a thorough checkup, knowledgeable people can still screen him for behavioral signs.  Ask him what he had for lunch. See if he knows what date (day, month, year) it is.  Have him do some simple arithmetic. If he can't do those things, it's time to get a scan.