FILE - In this March, 27, 2016 file photo, Shiite cleric Muqtada al-Sadr gives a speech to his followers before entering the highly fortified Green Zone, in Baghdad, Iraq. Al-Sadr, who led punishing attacks on American forces after the 2003 U.S.-led overthrow of Saddam Hussein, appears set to secure the most significant victory of his political career with a strong showing in the May 12 parliamentary election. Al-Sadr gained popularity as a nationalist voice campaigning against corruption and against Iran’s influence in the country. (AP Photo/Karim Kadim, File)
Shape-shifting Shiite cleric Moqtada Al Sadr has emerged as a potential king-maker after his bloc won a plurality of seats in Iraq's general elections. Karim Kadim / AP Photo

Who is Moqtada Al Sadr?