There is one obvious reason that George Bush did so badly in the debate: he wasn't wearing his usual earpiece connecting him to advisors in a back room. Prediction: Next time he'll be wearing it and everyone will be amazed at how much better he does...
An email to Meet The Press asking whether Bush wore an earpiece during the interview received a lightning quick response from Executive Producer Betsy Fischer: "The President was not wearing an earpiece at any time during the interview."
Was Bush wearing an earpiece during today's Meet The Press Interview? Consider the following excerpt (italics added):
Russert: "In light of not finding the weapons of mass destruction, do you believe the war in Iraq is a war of choice or a war of necessity?"
President Bush: "I think that's an interesting question. Please elaborate on that a little bit. A war of choice or a war of necessity? It's a war of necessity. We-- in my judgment, we had no choice when we look at the intelligence I looked at that says the man was a threat."
When Bush said "please elaborate on that a little bit" he did not appear to be asking Russert to elaborate the question. He seemed to be talking almost to himself. Perhaps he was just momentarily confused by an unexpected question. However...
If Bush was wearing an earpiece the odd statement makes more sense. An unseen handler would have had an excellent reason to say "please elaborate on that" to encourage Bush to give more of an answer than "I think that's an interesting question." Seen in this light, when Bush said "please elaborate on that" he mistakenly repeated an instruction from an unseen handler.
This one small incident alone is (obviously) not proof. But there have been others. Consider this quote from a December 15th press conference (italics added):
George Bush: "See, without the tax relief package, there would have been a deficit, but there wouldn't have been the commiserate -- not 'commiserate' -- the kick to our economy that occurred as a result of the tax relief."
Again... he could have just said "not commiserate" by mistake. But why? A less contradictory explanation would be that an unseen handler tried to correct him and instead of understanding the correction, Bush simply repeated what he heard in his earpiece.
Early in the Bush administration, commentators poked fun at his frequent verbal gaffes and his inability to accurately read a teleprompter. Then he seemed to improve. Perhaps Bush simply learned to speak more coherently.
But an earpiece connected to a room of unseen handlers also explains this change.