I started to write that "it boils down to 'he said/he said'", but it's not even that, Tom, it's just "he said" and nobody is backing him up and nobody's proving him wrong. It's in limbo, from which a reasoning mind could not possibly derive the adamantine certainty of "He never actually said that." Period. Full stop. Mind made up.

Yet, if it's implausibility that's causing the wave function to collapse for you, even that's a stretch. Has there ever been an American President who's not at least thought that sentiment? It's not beyond the realm of possibility that George W. Bush might experience a sentiment similar to that of his predecessors. Further, we know that Bush believes, rightly or wrongly, that in times of national threat, he has extra-Constitutional powers. That is, he's not a strict constructionist, and believes that the Constitution must bend to fit the circumstances (or his needs). He apparently does believe that it's "just a...piece of paper". Finally, Bush is much admired by Conservatives for his contemptuous "straight talk", and his many public gaffes provide ample evidence that his mouth is not always under his full control...is it not entirely plausible that in frustration he might blurt out his feelings? In a private meeting with Republicans likely to be sympathetic?

A reasoning mind would certainly conclude that it is indeed possible.