The Democrats have not moved quickly enough on some issues. The party seems to be divided between several power groups that don't have a unified goal and are fighting to set the agenda. Plus, many of the Democrats seem to think that if they give Bush enough rope he will hang himself.
I think many of the long time Washington types simply have not accepted the degree to which Bush and the cabal around him are actively trying to undermine the Constitution. The whole unitary executive thing is designed to move all of the real power to the office of the president.
In fact, a good case can be made that if not for Katrina, the cabal would be setting things up right now for Bush to retain power till the "war on terror" was over. It wasn't just the total incompetence of Bush's chosen agents, but the way it hammered home that Bush didn't care.
Jay