"If he does talk, even if it is all lies, and it connects to what Clarke said, it would be a political disaster and could be the end of the Bush presidency."
Oh sheesh, there were all these tell-alls before the election and they didn't do a thing to Bush. I think most people are smart enough to process this stuff for themselves. I think the amount of these books before the election if anything served to point out in peoples' minds the lengths Bush's enemies will go to in order to discredit him. Tenent will just look like another petulant child trying to take the blame off his shoulders.
Having the CIA director allege the stuff is MUCH, MUCH bigger than anything that has come out so far. Look how big Clarke turned out to be when he was just a little pissant.
You are seriously underestimating how serious a problem it would be if the CIA director at the time came out to attack Bush on 911.
It would be huge.