Is there some pattern here I don't know about? Bush wasn't obviously reading, so that kind of reading-based pronunciation error is probably out. Is Bush treating this (by analogy?) like -tion suffixes? Was he extending the pattern of affrication noted above? Is he really and truly not a competent speaker of English? What's happening?
Hey, I'm just trying to understand the world around me. And by the way, free Tibet.
Update, Thursday, 3:53. As the Ridger's comment below indicates, Mark Liberman has flat out answered this question, here. It in fact is a consistent oddity of Bush's idiolect. Wow.