Reminds me of an article I read in this week's Atlantic magazine about Bush vs Kerry in a debate. Talked a whole bunch about Bush's speaking style.
What stood out was how completely floored the author was when he went back and watched an old tape of a debate with Ann Richards. Appearently it was like watching a completely different guy.
Bush's accent wasn't there, but more significantly Bush spoke eloquently and lucidly. He was so shocked he brought in some kind of personality analyst to watch the tape. This guy too couldn't believe what he was seeing.
All sorts of theories about the transformation followed.