Supreme Council for the Islamic Revolution in Iraq
The Supreme Council for the Islamic Revolution in Iraq (SCIRI) is a Shi'a organization in Iraq, a combination of political party, social service group, and military wing called the Badr Corps; it had been a resistance group under Saddam Hussein. Under the new Government of Iraq, it is now the Islamic Supreme Council of Iraq (ISCI).
In May 2003, its long-term leader, Ayatollah Baqir al-Hakim returned to Iraq from exile in Iran. He entered at Basra on 10 May, and drove, in a large procession, to Najaf, which would become his headquarters.
While he had been sheltered in Iran, he did not consider the Iranian form of theocracy, wilayat al-faqih (the rule of the jurisprudent) appropriate for Iraq. He was a recognized marji' (Shi'a jurist and theologian), and had consulted with others, collectively called the marji'iyya, to form a distinct Iraqi style. In his model, the marji'iyya would be important, but would separate its political and spiritual roles. Among those consulted were Grand Ayatollah Ali Sistani, the leading marji' in Iraq, or marji' al-Taqlid.
Historically, the individual marji's had avoided politics, a very different situation than Iran. There were exceptions. The Islamic Dawa Party had acknowledged religious authority, primarily al-Khoei but retained the right to make political decisions. Sistani preferred a background role.
Hakim, however, wanted both roles. 
The Coalition Provisional Authority, in July, discussed whether to include SCIRI in the interim government, knowing it had ties to Iran. L. Paul Bremer decided to allow it into the political process, partially because Muqtada al-Sadr was a far more radical, but less organized, Shi'a. 
Baqir al-Hakim was killed, along with approximately 100 other Shi'a, by a bombing of near a shrine in Najaf. LTG Sanchez wrote that it became accepted it was set by Sunni extremists.