The Shiite coalition is widely expected to pull in the largest number of votes on election day.
Because of its strong showing in Baghdad and the south, the main Shiite coalition is on track to win at least 120 parliamentary seats.
One of the main stresses inside the Shiite coalition stems from a division over the group's choice for prime minister.
Recently left main Shiite coalition to run on his own.
That task would become much easier if the Shiite coalition fractures on its own, which appears possible.
The two leaders' political groups are part of a Shiite coalition contesting the elections.
A Shiite religious coalition won 48 percent of the vote and is expected to receive a slim majority in the assembly.
Though his political group has joined the Shiite coalition, he has yet to endorse anyone.
Protesters said that the elections were rigged in favor of the main religious Shiite coalition.
The slate trailed only the main Shiite coalition of parties.