Personally, I think he's just completely out of touch with reality. Being President will do that to you. Being this President, presiding over his disastrous policies at a moment when he has to pull some kind of defense for them out of thin air in order to be re-upped will really do that to you.
None the less, a case is being made around Blogville that there's something more at work here. The rumors have only been helped along by Bush himself who is refusing to take his annual physical this year for the first time in four years (usually he has it done in August). Add to that his miserable performances in the debates, his drooping lips, his drooling in last night's debate and various out and out bizarre moments over the past several months, and there's now talk of a stroke or pre-senile dementia.
This video compares the Dubya from 10 years ago to the Dubya today. There is a marked difference. You be the judge.
If they can waste your time by hoping to distract you with phony outrage about Mary Cheney being "outted" (Note to Fox News and other similarly "outraged" Fake Conservatives: you can't "out" someone who is already out!) then I can waste your time with this.