Shiite Cleric Sadr Emerges as Kingmaker After Iraq Election

BAGHDAD—Shiite cleric Moqtada al-Sadr, the onetime leader of a rebellion against U.S. forces following the 2003 invasion of Iraq, is poised to become the country’s key political power broker after his movement won the largest share of seats in Sunday’s parliamentary election.

The formation of a new government could be subject to weeks of political horse-trading with no clear leader in view. Mr. Sadr, an independent-minded nationalist, faces fierce competition from Shiite political rivals and pro-Iran hard-liners who wish to pull the country into closer orbit around Tehran.