(CNN) Anti-American cleric Muqtada al-Sadr's political coalition has won Iraq's parliamentary election, the election commission announced late Friday.
The Saeroon Alliance led by al-Sadr, the Shia who many US military officials hold responsible for the deaths of US troops, won by taking the most number of seats in the May 12 parliamentary elections.
Moments after the results were announced Friday, al-Sadr tweeted, "Your vote is an honor for us." He added, "Iraq and reforms have won with your votes...We will not disappoint you...the blame, all the blame is on those who failed Iraq."
The Saeroon Alliance claimed 54 of the 328 seats in the parliament, the most of any coalition. The Fatah Alliance, led by Hadi al-Amiri, took 48 seats, while the Victory Alliance, led by Washington's preferred candidate, Prime Minister Haider al-Abadi, won 42 seats.
Al-Sadr, who in 2008 was named as one of Time Magazine's 100 most influence people, campaigned on an anti-corruption platform, allied himself with the Communist Party and rode a wave of populist sentiment to victory. An opponent of Iranian influence in his country, al-Sadr is also a longtime foe of the United States and its role in Iraq.
Al-Sadr was once the leader of the Mehdi Army, a powerful Shia militia, which was blamed for some of the worst violence between 2005 and 2008 in Iraq. Some of his militiamen fought and killed US and Iraqi soldiers. He formally disbanded the group in 2008, announcing that it was transitioning into a movement to oppose secularism and Western thought.
Under the power-sharing system installed after the 2003 US-led invasion, the position of prime minister is reserved for a Shia. Abadi, who's been in power since 2014, hoped to retain the top job, but Iraq's Shia bloc has splintered into five major coalitions.
Al-Sadr will still need to reach out to other blocs, including Sunni and Kurdish coalitions, to form a governing alliance.
While Iraqis have celebrated the routing of ISIS fighters from major cities in the country's north, they are also frustrated by the limited change they've seen in their daily lives.
Among their complaints are a dearth of job opportunities, a struggling economy and a crumbling infrastructure with frequent power cuts. They also lament poor government services and slow reconstruction in areas such as Tikrit, Falluja and Mosul, places that were ravaged in the fighting against ISIS.
Corruption, another major issue, is blamed by many Iraqis for their country's failure to translate the wealth from its natural resources into a better life for all its citizens.