The greatest wildcard is 78-year-old Iranian-born Grand Ayatollah Ali Sistani. He is Iraq's leading religious figure and possesses significant implicit political clout. Like many traditional Shia clerics, Sistani sees his role as an indirect guide rather than an active political leader. While he advocates Shia empowerment, he tempers populist anger, discourages Iranian-style clerical political control and eschews violence. When he dies, it is unclear who might fill his role. Najaf is home to other Grand Ayatollahs – Afghan-born Muhammad Ishaq Fayadh and India-born Bashir Najafi – but neither has a large enough following to replace Sistani.
Many senior Shia leaders live in Iran but to prevent even passive challenge to Iranian Supreme Leader Ali Khamenei, the most prominent traditional clerics in Iran – Hossein Ali Montazeri and Hossein Kazemeyni Boroujerdi – remain under house arrest or in prison. At best, should Sistani die in the near future, there will be no clear marja at-taqlid (source of emulation), to represent the Shia voice. In such a situation, firebrands such as al-Sadr may find little impediment to religious demagoguery.
Alternatively, 73-year-old Iraqi-born Grand Ayatollah Muhammad Hussein Fadlallah may return from Lebanon. While scholars debate whether or not Fadlallah is a patron for Lebanese Hizbullah, they do not debate either his long association with the group nor his support for their actions. Should Fadlallah return, no cleric is likely to be able to challenge him as the pre-eminent Shia religious authority in Iraq. As much as Sistani has been a voice for calm, his successor could become a force for discord.
As long as Iraqi security is dominated by personalities rather than checks and balances, stability in the country will be a mirage. The situation in Baghdad has improved greatly since 2007, but while success rests upon the longevity of old men and unwillingness to acknowledge the prime minister's mortality, any gains could fast reverse.