Isn’t the real question one of why didn’t the Republican “leadership” effectively counter the lies about the causation instead of letting the Democrats and their media cohorts constantly reiterate about the “failed policies of Bush?”
Two things really...
1st: most politicians will use any leverage they can get> If the prevailing wind blowing is one of The President is responsible for "x" most politicians no matter what the party will take the same stance, just ion varying degrees depending if they are in the same party.
2nd: If the Media is all in lockstep promoting a cause/story/template such as: "Bush Policies are a failure" then there is really no point in refuting it on those networks or in those newspapers because those MSM critters will just target those who challenge their template and call them liars etc.
Truth really has no bearing on the issue, if you speak a lie often enough it is accepted as truth. Witness man-made globull warming so many lies spoken over and over it is now accepted as truth by a large portion of the population.