Porter Goss: Mission Impossible
I don't think the general public or even most conservatives yet appreciate just how hostile the CIA is to Republicans in general and to Bush specifically. If you wanted to move out everyone whose political bias against Bush affects their job performance, you would have to fire 3/4 of the agency.
Liberals have very successfully dominated the entwined worlds of gov't agencies, journalism, and academia through a de facto system of preferential hiring and outright blacklisting. It will take at least a generation to bring a reasonable balance to any of those three, if such a change is even possible. We are doing next to nothing to effect such a change today.