A Shia cleric whose militia once fought US forces during the Iraq insurgency has won Iraq's parliamentary election.

Muqtada al-Sadr, former leader of the infamous Mehdi Militia, fashioned a coalition of extremist Shias, communists, and nationalists to gain 54 seats in the 328 member parliament, giving him a shot to form a larger coalition that would govern Iraq. Prime Minister  Haider al-Abadi's governing coalition finished 3rd, garnering only 42 seats.

CNN:

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.

To have an anti-American extremist leading Iraq at this time is very bad for the US. Iraq borders Syria and Iran and it's unclear how much cooperation with the US will be forthcoming with Sadr pulling the strings of government. 

But Iraq's security depends heavily on the US. Sadr would be stupid to kick the US out of the country entirely, no matter how anti-American he proclaims himself to be. 

There are currently about 4,000 US troops in Iraq, plus special forces and CIA paramilitaries. Their mission is devoted to rooting out remaining ISIS fighters and making sure the terrorists don't rise again. The US military has a good relationship with the Iraqi army, having trained most of its best units. 

But the biggest question is how much the Iraqis will help in putting pressure on Iran and Syria? Prime Minister Abadi was reluctant to host special forces units who operated in Syria so it is unlikely that this will change under Sadr. It is also unlikely that any military action against Iran by US forces would be supported from Iraqi soil.

Sadr, whose militia killed dozens of Americans during the insurgency, will be an unpredictable element in an unpredictable region.