ISCI is the Iraqi faction with the longest and closest ties to Iran. Baqr Al Sadr was hung by Saddam Hussein in 1980 at the start of the Da'wa Party rebellion against Saddam's regime. Iranian Support to Armed Groups

Iran's arming and training of Shiite militias in Iraq added to U.S.-Iran tensions over Iran's nuclear program and Iran's broader regional influence, such as its aid to Lebanese Hezbollah and the Palestinian organization Hamas (which controls the Gaza Strip). U.S. officials feared that, by supplying armed groups in Iraq, Iran was seeking to develop a broad range of options that included: pressuring U.S. and British forces to leave Iraq; to bleed the United States militarily; and to be positioned to retaliate in Iraq should the United States take military action against Iran's nuclear program. In 2007, a press report said there are 150 Qods and intelligence personnel there, but some U.S. commanders who have served in southern Iraq said they believed that there were perhaps one or two Qods Force personnel in each Shiite province, attached to or interacting with pro-Iranian governors in those provinces. Since January 2008, the Treasury Department has taken action against suspected individual Iranian and pro-Iranian operatives in Iraq by designating them as a threat to stability in Iraq under a July 17, 2007, Executive Order 13438. However, Iran has always sought alternate channels to continue to influence policy in Iraq and protect its interests there, and influencing senior Iraqi political leaders has been a cornerstone of Iran's policy. In the end, Iran's concerns were attenuated by a provision in the final agreement (passed by Iraq's parliament on November 27, 2008, and in force as of January 1, 2009) that U.S. forces could not use Iraqi territory as a base for attacks on any other nation. Iranian Political Influence Following the January 31, 2009, Provincial Elections

During 2009, Iran's political influence in Iraq was further jeopardized by widening political rifts among the pro-Iranian Shiite factions. ..." Still, the report also said that Iran "continues to pose a significant challenge to Iraq's long-term stability and political independence ..." and that "Iran continues to support Sadr's religious studies in Qom, Iran [where Sadr is believed to have been for at least a year]." Iranian Efforts to Influence the March 7, 2010, Iraqi Elections

Perhaps seeking to restore its influence, Iran set out to try to shape to Tehran's advantage the Iraq's 2010 national elections for the National Assembly, which chooses the next four year government. Some viewed it as an independent effort by elements of Iran's Revolutionary Guard to assert themselves in the Iran-Iraq border regions.
With a conventional military and weapons of mass destruction (WMD) threat from Saddam Hussein's regime removed, Iran seeks, at a minimum, to ensure that Iraq can never again become a threat to Iran, whether or not there are U.S. forces present in Iraq. Some believe that Iran's intentions go far further—to try to harness Iraq to Iran's broader policy goals, such as defense against international criticism of and sanctions against Iran's nuclear program, and to enlist Iraq's help in suppressing Iranian dissidents located inside Iraq. Some believe Iran sees Iraq primarily as as providing lucrative investment opportunities and a growing market for Iranian products and contracts.
Iran has sought to achieve its goals in Iraq through several strategies: supporting pro-Iranian factions and armed militias; attempting to influence Iraqi political leaders and faction leaders; and building economic ties throughout Iraq. It is Iran's support for armed Shiite factions that most concerns U.S. officials. That Iranian activity continues to a threat to stability in Iraq, according to senior U.S. commanders, and positions Iran to pursue its interests in Iraq after U.S. forces leave Iraq by the end of 2011.
Many of Iraq's current leaders were in exile in Iran or materially supported by Iran during Saddam's rule, and see Iran as a mentor and an influential actor in Iraq. Even those who have longstanding ties to Iran have asserted themselves as nationalist defenders of Iraqi interests, but Iraq appears to be a clearly subordinate partner in the relationship. Perhaps resenting this relationship, many Iraqi citizens have appeared to reject parties and factions who accept preponderant Iranian influence in Iraq. This sentiment has caused Iran to suffer key setbacks in Iraq. The most pro-Iranian factions generally fared poorly in the January 31, 2009, provincial elections and again in the March 7, 2010, national elections for the National Assembly, which chooses the government. A political bloc that is decidedly against Iranian influence and which is supported by Iraq's Sunni Arabs won the most seats in the election, although no bloc has been able, to date, to build enough support among other blocs to assemble a government. Still, virtually all political blocs are consulting with Iran to try to gain its support for their inclusion in or dominance of any new government.
Also see CRS Report RL32048, Iran: U.S. Concerns and Policy Responses, by [author name scrubbed].