Why can't he hold a glass of water?

[GoCubsGo]

4. I'm going with "stroke", but others have made a good case for other reasons, too.

Dementia, various degenerative cervical spine/nerve diseases, and carpal tunnel syndrome have been mentioned. I could see any of them being at the root of this, including the latter, considering how much of his time is spent typing in tweets on his phone. I'll add another possibility: His muscles are so atrophied from not exercising that he doesn't even have the strength to pick up a glass of water. Also notice that he does a lot more seated "round table" discussions, rather than stand-up press conferences. Is he so out of shape that he can't stand up for more than a few minutes at a time?