Iraq's political, ethnic and sectarian groups saw the December 2011 U.S. military departure as an opportunity to grab for power. Even Iraqi Prime Minister Nouri al-Maliki tried to capitalize on the U.S. departure, as evidenced by his attempted arrest of Vice President Tariq al-Hashimi, the country's highest-ranking Sunni official, on terrorism-related charges. Al-Hashimi evaded arrest by fleeing to northern Iraq's Kurdish enclave, under the auspices of Iraqi President Jalal Talabani.

The incident has created a standoff between al-Maliki's Shia-dominated government and the country's Sunnis, represented by the al-Iraqiya bloc, and has exacerbated tensions between the Iraqi and Kurdish governments. It has also exposed rifts between al-Maliki and the movement led by Iraqi Shiite leader Muqtada al-Sadr, which holds more seats in parliament than any other Shiite political group.

While the Sunnis have sought Turkish and U.S. political assistance in the matter, Ankara and Washington have markedly less influence in Iraq than Tehran. In fact, Iran has been trying to assuage tensions in Iraq, as shown by its appointing senior Islamic Revolutionary Guard Corps-Quds Force commander Gen. Sardar Majidi to mediate the Sunni-Shia standoff. The challenge for Tehran is to ensure a resolution of the current crisis without empowering the Sunnis.

In similar past situations Iran has played one faction off the other, maintaining its influence over Iraq's Shia community without weakening the Shia position overall. Despite being competitors, both al-Maliki's and al-Sadr's factions realize they need to work with one another. But the current situation is slightly different than those of the past. Iran not only has to secure Shiite unity but also make sure al-Maliki's moves against the Sunnis do not go too far. Iran cannot afford to alienate the Sunnis entirely, especially with so much uncertainty in Syria. Should the Alawite government in Damascus give way to Sunni government — or if there is anarchy — Iraqi Sunnis could feel so empowered as to confront the Shia who currently dominate Baghdad.

Unchecked instability in Iraq is not in Iran's interest, especially now that Tehran's influence in Syria is threatened. In truth, the current situation in Baghdad is ideal for the Iranians, considering it took nine months for Iraqis to create a government after the March 7, 2010, parliamentary elections. However, managed Iraqi instability is useful for Iran because it keeps Iraq within Iran's sphere of influence — and because it can be used as leverage against the United States. But if such instability threatens Shia political domination, Tehran would have to intervene to ensure that its foreign policy interests were not undermined.  

Another problem is that Tehran's interests differ from those of its various Shia proxies. While Iran certainly has influence over Iraq's Shia community, this influence is limited by differences within Iraq's Shia factions. In fact, the leaders of Iraq's two main Shia factions, al-Maliki and al-Sadr, on several occasions have tried to free themselves from Iranian influence. Al-Maliki attempted to do so when he formed the State of Law coalition and contested the parliamentary elections independently of the Iraqi National Alliance. As al-Maliki tightens his control over Iraq — he is the acting interior minister, defense minister and national security chief — Iran is careful not to see him become too powerful or allow him to upset the balance Tehran has been trying to maintain.

Interestingly, Iran was instrumental in al-Maliki's winning the Iraqi premiership. He was able to win the post because of his post-election partnership with the Iraqi National Alliance. This partnership formed a super Shia bloc that collectively won 159 seats, allowing al-Maliki to prevent his biggest rival, al-Iraqiya leader Iyad Allawi, from becoming prime minister. The Iranians were heavily involved in this post-election engineering.

Al-Maliki also was aided by support from his Shia rivals, whom he could not afford to alienate. If his Sunni opponents were to somehow persuade these opponents to abandon their support of al-Maliki, they might be able to remove him. But al-Maliki is betting his rivals will refrain from going that far, lest they want to undertake the daunting task of forming a new government. This gives him much leverage. Already he is operating outside parliamentary bounds by establishing an executive branch with sweeping powers, which is exactly the type of scenario Iran wants to avoid.

Iran has the option of working with the Kurds, who also have close ties to Tehran. However, if the Sunnis realize that the Iranians and their Iraqi Shia allies are on the defensive, they will try to gain more political power. In essence, the Iranians would have to oversee a fresh power-sharing understanding in Baghdad.