Hold the elections and then declare victory and GTFO. There are too many factions, and eventually, it will crumble into civil war anyway. Why spend more American lives propping up a regime that will fall? Let them get back to killing each other instead of Americans.
Alternatively, split Iraq into three extremely semi-autonomous regions: Sunni, Shi'ite, and Kurd. They'll still fight each other, but maybe not on a daily basis.
We're fighting not only the insurgents, but almost 1500 years of Middle Eastern culture and history, none of which deals with freedom or democracy. It's not going to happen in a day, a year, or a decade, folks. How much do you want to pay, in terms of lives and capital?