The calculation was simple: after decades of rule by the minority Sunni Arabs, the majority Shiites could seize power if enough voted.
The deadlock over the interim constitution had pitted the country's majority Shiites against its Kurdish minority in the north.
One of the biggest questions at day's end was the role of most of the majority Shiites previously thought to be relatively sympathetic to American goals.
Each country's majority Shiites revere the other's clerics and visit the other's religious shrines.
Last year, majority Shiites staged widespread riots after a security crackdown by Sunni rulers.
Bahrain's majority Shiites began an uprising in February seeking greater rights from the kingdom's Sunni rulers.
The turnout, and loud celebrations, were widespread among the majority Shiites in the region.
But the day may come in Iraq when the majority Shiites save the victory that President Bush is seeking to preserve against a rain of reversals.
The appeals have been counterbalanced by demands from the leaders of Iraq's majority Shiites that the elections go ahead.
The government took three months to assemble, as the majority Shiites, who took power for the first time, negotiated with Kurds and Sunnis over its composition.