According to
http://www.cnn.com/2006/POLITICS/12/14/johnson.ill/index.html, Senator Tim Johnson (D-SD) has suffered a brain hemorage.
If he were unable to serve as Senator, the new majority leader could actually be Sen. Mitch McConnell (R-KY) instead of Sen. Harry Reid (D-NV). South Dakota Governor, Mike Rounds, a Republican, would likely appoint a Republican replacement for Johnson, thus bringing the Senate to a 50-50 tie and giving Vice President Dick Cheney the tie-breaker.
Certainly, we wish Johnson and his family the best, but how big of an impact would that one seat shift have on the new Congress?