His [Bush's] major goals are to prevent criminal prosecutions of himself (unlikely in any event) and his aides (more likely), to keep the public from finding out much of what he and his advisors actually did and ordered done during his presidency (his fight for immunity for telecom companies who engaged in illegal surveillance should be understood as part of this larger strategy), to entrench the U.S. presence in Iraq for the foreseeable future, and do what he can to ensure that John McCain becomes President, or failing that, Hillary Clinton as a second best solution. He figures that McCain, and, to a lesser extent Clinton, are most likely to continue aspects of his policies and keep troops in Iraq for some time. The longer that the next president continues his policies-- including warrantless surveillance, his interrogation practices, and his war in Iraq, the longer these features will become normalized and/or the next President's problem.
How much of this expanded executive power would Hillary hold on to? The Clinton's excessive secrecy to date means more of the same for the next four or eight years.
H/t Dan Froomkin