Iraq’s Shiites, although the majority, are fractured into competing political parties. Since Saddam Hussein’s ouster in 2003, Shiite coalitions have run the government, a formula still considered key in this election.
The backlash to Mr. Abadi’s move was swift.
The Iranian-backed Shiite militias have won praise for helping defeat the Islamic State, but they have also been accused in sectarian atrocities and their leaders are seen by many as tools of Iran. Sunni and Kurdish leaders were furious. Even a Shiite leader, Moktada al-Sadr, a possible kingmaker in this vote, called the alliance “abhorrent.”
Within 24 hours, Mr. Abadi had reversed himself, and the militia leaders left the coalition.
Mr. Abadi’s blunder was a stark reminder of the fact that, with the election still more than three months out, nothing can be taken for granted.
While he is still Iraq’s most popular politician and front-runner, Mr. Abadi’s clumsy outreach and deal-making have compounded his difficulties, alienating the influential factions he needs to win.
“Abadi has a narrow line to walk,” said Renad Mansour, an Iraq analyst at Chatham House. “He is popular among many types of Iraqis, but he also has serious enemies. Politics is about shared power in Iraq.”
Mr. Abadi took power in 2014, shortly after the devastating Islamic State blitzkrieg occupied one-third of Iraq and enslaved tens of thousands of his countrymen. Most Iraqis attribute that disaster to the failings of his predecessor, Nouri al-Maliki, who ruled for eight years before being ousted by his own Shiite coalition in favor of Mr. Abadi.
But while Mr. Abadi is the leader of the nation, he does not head his own political party, the Islamic Dawa — making his political position precarious. The party’s leader remains Mr. Maliki, who despite his checkered political past is itching for a comeback.
So in a classic example of the serpentine nature of Iraqi politics, Mr. Maliki has blocked Mr. Abadi from using Dawa resources for his campaign.
Mr. Abadi created his own coalition, the Victory Alliance, the one to which he first welcomed, then removed, the pro-Iranian militia leaders. The coalition immediately attracted dozens of national and regional politicians from across sectarian lines, giving his aides confidence in a strong platform to enter the election season.
Iraq’s postwar Constitution reserves the position of prime minister for a Shiite. Given the country’s history of tight elections and coalition governments in the three national polls since Saddam Hussein’s ouster in 2003, Mr. Abadi needs an alliance with at least one of three major bulwarks of Shiite political power to win, analysts say. (The largely ceremonial presidency is held by a Kurd, and the speaker of Parliament is a Sunni.)
The problem is that these Shiite powers all have their own baggage. One is Mr. Maliki, a politically damaged rival who wants the job himself. Another is the pro-Iranian militia leaders, who are close to Iran’s Revolutionary Guards, a liability that has already backfired on Mr. Abadi.
And the third is Mr. Sadr, a populist firebrand who has become a champion of the poor and unemployed and a fierce opponent of Iranian meddling.
Mr. Sadr, best known to Americans as the thuggish militia leader who for years after the United States invasion fought and killed Americans, has become a pro-Arab, anti-Iranian nationalist. He is running his own coalition which, like Mr. Abadi’s, is cross-sectarian. It includes Sunni leaders who welcome Mr. Sadr’s anti-Iran message.
Politicians close to Mr. Abadi had been in exploratory talks with Mr. Sadr’s followers about joining with them in a possible coalition. It is not clear why those talks foundered, but Sadrists say their leader was angered by Mr. Abadi’s alliance with the pro-Iranian militia leaders.
Even Mr. Abadi’s closest advisers now concede that alliance was a serious tactical error, which they attribute to the overwhelming task of setting up a new political entity on short deadline.
Registration for the election ended Jan. 15.
“We did not have time to finalize who our main partners would be, what we stand for and what we all agree with,” said Ali al-Adiib, a member of Parliament close to Mr. Abadi. “We are discussing all these things now.”
Some analysts say the prime minister’s reputation may be forever tarnished.
“The latest developments undermine the view in Washington that Mr. Abadi is a bulwark against sectarian forces with strong links to Iran,” wrote Hassan Hassan, a counterterrorism author, in an opinion piece published in Abu Dhabi-based newspaper The National.
Others say it’s too early to make predictions this far in advance given Iraq’s unpredictable security climate.
One way Mr. Abadi could bolster his reputation, especially among Iraq’s Sunnis, is a successful performance at an international donor’s conference next month in which his government is hoping to attract hundreds of billions of dollars in aid to rebuild the mostly Sunni cities destroyed during military operations against the Islamic State.
The United Nations estimates that around 2.6 million Iraqis, mostly Sunni Arabs, remain displaced after the fighting and utter devastation of their towns.
Leading Sunni and Kurdish lawmakers argued last week to delay the election, saying that a fair vote would be impossible because so many Iraqis were still scattered and their regions lacked infrastructure for a vote.
On Jan. 21, Iraq’s Supreme Court ruled that a delay would be unconstitutional.
Wathiq al-Hashimi, the head of the Iraqi Group for Strategic Studies, believes that, despite the challenges, Mr. Abadi has the best chances of victory for a simple reason: the optimism he restored to Iraqis after beating back the Islamic State.
“The path for Abadi’s second term will be one strewn with flowers,” he said.