Ron Brownstein writes in his Saturday L.A. Times column:
At the same time, the war's changing nature undermines the argument from many on the left that the U.S. presence is primarily fueling the violence. That seems increasingly untenable at a point when U.S. troops look like the only thing preventing Iraqis from tearing each other apart.
In this murky and volatile period, the analysts who look most prescient are those, like Sen. Carl Levin (D-Mich.), who have insisted that the U.S. use its leverage in Iraq to pressure all sides to reach political accommodations. U.S. Ambassador Zalmay Khalilzad has grown more forthright in sending that message too.
Bush now faces a paradox. As Iraq pulls apart, its need grows for American troops to serve as buffers and brokers. But as the sectarian violence rises, so will the pressure inside the U.S. to withdraw. However reluctantly, most Americans have not yet entirely abandoned the hope of building the Arab world's first functioning democracy. But they will probably show much less patience for watching American soldiers die in the next Lebanon.
As Iraq Conflict Changes, Has Bush Kept Up? - Los Angeles Times
Well, maybe, but it isn't like U.S. troops actually did anything to stop the violence (unless they were secretly sprinkling magic dust). They were, quite explicitly, ordered to stay in their barracks while the fighting raged (See the excellent http://www.juancole.com/ on this).
The only difference between being there and letting the Iraqis "tear each other apart", and leaving and letting the Iraqis "tear each other apart", is that in the second case U.S. troops don't get caught in the cross-fire.
No, this is another war-mongering guy's attempt to salvage a situation where the war he mongered for has turned to shit in his hands.