Note to Media:  I know it would be an amazing turn around if Tim Johnson's illness would flip control of the Senate back to the GOP, but somebody stop and think for a minute. 

To the best of my knowledge its not up to anyone but Sen. Johnson as to whether or not he is "incapacitated" and unable to serve out the rest of his term.  I don't think you'll find any document, be it the federal or South Dakota state constitution, that defines "incapacitated" or gives another official or politician the power to declare a sitting member of Congress incapacitated. 

Want a recent example of an "incapacitated" politician?  How about Strom Thurmond?  The Senator from South Carolina spent his last few years on life support at Walter Reed Medical Center except when they wheeled him out to vote, and even then the inside joke was that his mental capacity was so limited he rarely knew what he was voting for.  At his age it was considered a novelty that he was breathing and his staff worked overtime to make it look like he was actually performing his duties but I don't remember any move to remove him.  There are so many examples of long serving politicians holding on through illness like this and only leaving when they die so do us a favor and chill out.