Clinton and Obama are not talking complete withdrawal, but more along the lines of withdrawing down to 40,000 to 50,000 troops who will remain to "protect" the bases (not "permanent" of course, just not set to be dismantled at any particular date).  What we've been witnessing is increasing air "support" similar to the tactics in Vietnam, only these folks aren't Buddhists, and they have their own intractable, centuries old nefarious feuds just waiting to be "resolved" in their own unique ways.  One of those ways appears to be a Daisy Chain of shifting support of the different groups for each other, with some of the Sunnis who have been targeted by Sadr's Mehdi people, driven from their homes in Baghdad, somewhat aligning with the Mehdi against Maliki and ISCI who want Sadr and his large political following defused by this new version of an ever brewing civil war.  

(Americans' conceptual problems are anchored in the cognitive drawback that they can culturally only conceive of binary oppositions for a civil war, so much of this is beyond the media's ability to express.)

Drawing down to lower troop numbers Democrat candidates are willing to acknowledge, bunkered down in the five or six "indefinitely" established bases, will be contingent on whatever circumstances happen to be in place, circumstances determined by politically impossible to resolve, and never ending differences, and I'd wager whoever is in the White House will find those contingencies unacceptable to the ordering of a stand down, since the stand up by any strong enough group of Iraqis is not likely -- unless that president happens to be McKinney or Nader, and what's the chance of that?  (That's rhetorical, no one needs to answer that.)

Meanwhile, this administration's wrecking ball continues to swing, and we are headed into a possible if not probable depression before it's lame duckness is finally, mercifully ended, since the other means of ending it is off the table.

: Rebuilding the American Economy, Bush-style -By Tom Engelhardt  

Desiring-machines work only when they break down, and by continually breaking down. - Deleuze & Guattari