Conservatism, not Bush, is the problem
The political angle is this: if we call Bush incompetent, that does nothing to damage the political philosophy he represents. People might think that the next Republican will do better, and vote for him (unless it’s Rice, in which case it will be her). We must instead show that it is conservative governing principles themselves that are at the root of our problems.
And yes, many “conservatives” criticize Bush for not being a “real conservative”, but Bushism is conservatism as it currently exists and is practiced in this country. There may be some philosophically pure “conservatism” out there in the ether that has nothing to do with Bush and the Republicans, but it is not relevant to what is going on today. Maybe Stalin wasn’t a “real communist”, but as far as what the world needed to actually deal with, Stalinist communism was communism.