Let's be deadly clear: the strategy America has pursued since the fall of Saddam CANNOT WIN.
What will happen is what IS happening: the country will fray due to sectarian violence and score-settling, and US casualties will go higher and higher and higher as the US haplessly tries to separate people who want to kill each other.
Eventually...not in 2006, but in 2008, or perhaps in 2012 (because the war will never end for as long as we fight it this way), American domestic resolve to continue to lose our own boys and girls, and to have five maimed for every one killed, in a forever war will collapse. The Democrats will be elected, they will cut the funding, and the Americans will pull out of Iraq in disgrace...just like Vietnam.
To AVOID this, to WIN the war, we need to get out of the way and let the Shi'ites destroy the Sunni Arabs, who have always been our enemies in that country. We need to favor some Shi'ite factions over others. It's the only way.