BAGHDAD — Shiite coalitions that won the most seats in Iraq's May 12 legislative elections are absorbed in negotiations to form the largest parliamentary bloc, which will have the constitutional right to nominate the next prime minister.

The Sairoon Alliance led by Muqtada al-Sadr won the highest number of seats, but not enough for a parliamentary majority, so pacts must be made.

The main Shiite party, the Islamic Dawa, has led the country since 2005, but its two most powerful figures are bitter rivals. This year, their rift split the party into two coalitions, or lists: the Al-Nasr Alliance led by Prime Minister Haider al-Abadi and the State of Law Coalition led by party secretary and former Prime Minister Nouri al-Maliki.

Reuniting the lists has become a challenge. Abadi and Sadr have discussed forming an alliance. If that happens, Abadi would most likely have to distance himself from Dawa. If the two Dawa blocs were to reunite, Abadi — and Dawa — would lose a connection to Sadr, whose alliance was the leading vote-getter. One of Sadr’s main conditions is to exclude Maliki from any alliance.