Other than pure political calculation, Hillary has other reasons to tread carefully on Iraq.  Critics of the war tend to point to two things: faulty intelligence before the war and mismanagement during the war.  We’ve heard from Clinton on the latter, but we won’t hear much about the former.  If she goes after Bush for faulty pre-war intelligence then she’ll de facto be going after officials in the Clinton administration, who had the same info on Iraq.  She needs the Clinton machinery behind her to win the Democratic nomination, so don’t expect her to be stepping on toes anytime soon.