Fred99:
A bit of a legal minefield of course - what the hell is a "misdemeanor" - or what the hell was a misdemeanor when that was written?
The 25th amendment is to deal with presidential succession (in case of the president being removed from office or incapacitated)
It's in the news because section 4 of the amendment deals with what happens when the president is unable to discharge his duties, the argument that Trump may have lost his marbles - thus that clause may be a means to get rid of him.
This might interest you: