Here's the full quote section on this meaning:
1592 W. WYRLEY Armorie 23 The Scriptures of God, the decider of all controuersies. 1764 FOOTE Patron I. Wks. 1799 I. 329 The paragon of poets, decider on merit, chief justice of taste. 1862 WILBERFORCE Let. in Life III. 106 The..danger of having..the Irish Bishops made the actual deciders of our doctrine.The 1592 quote probably gets at a core point about Bush -- he's assuming the powers of the Almighty, some would argue. But the 1862 might be a little farther than from current meaning. Note, though, that both have it with a definite article. Probably not enough to derail it as a WotY candidate, but it's always worth paying attention to history.
Sorry for the screw-up ... you folks who do 'scholarship' or 'journalism' have to worry about getting stuff right, but I'm learning that bloggers (except for the superstars over at Language Log), seem to operate more like Fox News or Bill Safire or something. I promise I'll be more careful in the future, little less like Stephen Colbert.
Or maybe the world needs a Matt Drudge for language!