I suspect that he may be physically capable of being cared for at home, but is not capable of speech or active participation in any way. Perhaps severely mentally handicapped right now and trying to prevent any kind of appointment to replace him.

He is not up for reelection I believe and intended to only complete his current term. There is a deadline to get on the Novemberballot and perhaps they are trying to reach that deadline to stop it being taken by a DEM.