People in Iraq voted Saturday in the first parliamentary elections since the country declared victory over ISIS terrorist group.
Turnout was 44.52 percent with 92 percent of votes counted, the Independent High Electoral Commission said - that was significantly lower than in previous elections.
The strong showing could be a testament to al-Sadr's loyal base of followers he maintains who cast their ballots despite a general mood of apathy that kept many Iraqis away from the polls.
In a further political upset, a rival bloc of pro-Iranian former fighters appeared to be coming in second, squeezing internationally favoured prime minister Haider al-Abadi into third.
The surprisingly strong showing of a ticket backed by maverick Shi'ite cleric Moqtada al-Sadr in Iraqi elections over the weekend will force United States officials to recalculate how best to pursue American interests in the region at an especially sensitive moment. Sadr portrays himself as an Iraqi nationalist and is tired of Iranian support, thus he will be cautious of prompting a pro-Iranian figure.
Sadr, whose forces fought USA troops in 2004, appears to be the big victor in Iraq's parliamentary elections, according to media reports.
A rival Shiite coalition headed by Nouri al-Maliki, who was pressured by Washington to resign as prime minister in 2014 after ISIS seized control of the country's west and north, won just 25 seats.
Sadr's father, highly respected Grand Ayatollah Mohammad Sadeq al-Sadr, was murdered in 1999 for defying Saddam Hussein. After the 2003 U.S. invasion, Mr Al Sadr formed the Mehdi army militia to fight American troops and later commanded his paramilitary forces against ISIS. He led two uprisings against US troops, prompting the Pentagon to call his Mehdi army the biggest threat to Iraq's security.More news: Avengers: Infinity War Just Opened To Huge Numbers In China
As for the Kurdish parties, they are competing at a time of divisions and changes in the Kurdish political landscape. His father's cousin, Mohammed Baqir, was killed by Saddam in 1980.
After the announcement that the Marching Towards Reform was ahead in Baghdad, supporters took to the streets in the capital to celebrate early on May 14.
The US-led coalition that helped battle IS pledged on Sunday to work with the elected government to ensure the "lasting defeat" of IS and said the poll proved Iraqis "emphatically rejected violent extremism".
Recently, he rebranded himself as a nationalist, anti-U.S. and anti-Iran.
Iraqi Communist Party secretary Gen. Raed Fahmy told Reuters the vote in favour of Sadr's list, backed by his group, "is a clear message that we must have balanced relations with all [countries] based on non-interference in Iraq's internal affairs".
"This gave him more supporters than he had before", Mayali added.
Tensions in the region have mounted - and in particular between the United States and Iran - partly because of President Trump's decision last week to withdraw the United States from the nuclear deal with Tehran.