BBC News Online profiles the Shia Daawa Party as part of a guide to the key players in post-Saddam Iraq.
The Daawa Party is one of the two biggest Shia political parties in Iraq.
Daawa's Ezzedine Salim was assassinated
Founded in the 1950s, it is the oldest of the Shia Islamist movements.
After a series of attempts to assassinate Saddam Hussein and some of his ministers, it was harshly suppressed and the group eventually split into several factions.
A senior Daawa figure, Sheikh Mohammed Nasseri, returned to southern Iraq from exile in Iran shortly after the fall of Saddam Hussein, as part of an attempt by the party to re-establish itself after years of clandestine existence.
Party spokesman Ibrahim Jaafari, a medical doctor, has been appointed one of the two vice presidents in the interim government established in June 2004.
He was a member of the Iraqi Governing Council before that.
Ezzedine Salim, leader of a breakaway faction of the party which drew most of its support from his hometown of Basra, was killed in a bombing in May 2004 when he held the rotating presidency of the Governing Council.
Analysts say the Daawa Party continues to suffer from fragmentation, and may have lost some support because of its co-operation with the occupying forces in Iraq.