Ali al-Sistani, a Najaf-based ayatollah who is probably the most widely revered scholar among the world's Shias today, has stated that in order to be legitimate such a ruler should win acceptance from a majority of believers.

ECONOMIST: A debate rages about the nature of clerical rule

Najaf is the seat of the Shiite clerical establishment and home of its foremost religious leader, Grand Ayatollah Ali al-Sistani.

NPR: The Mood in Najaf, Shiite Stronghold

The latest sign of this was the assassination attempt on Grand Ayatollah Seyed Mohammed Said al-Hakim, a leading Shia Muslim cleric, in the Iraqi holy city of Najaf on Sunday.

ECONOMIST: Iraq's security void