Just when it seemed the situation in Iraq couldn't get any worse, the government moved a step closer to collapsing into chaos on Sunday when its president, Fuad Masum, formally nominated a candidate to replace the country's authoritarian prime minister, Nouri al-Maliki, in an effort to break the political paralysis gripping the country since parliamentary elections in April. From there, things went straight downhill.

President Masum named Haider Abadi, a member of Mr. Maliki's own Shiite Islamist Dawa Party, as the next prime minister, urging him to forge a broad coalition government to unify the country against Sunni extremists who have taken over large swaths of Iraq in recent weeks and are threatening to march on the capital. But late that evening Mr. Maliki defiantly rejected the president's call to step down and ordered tanks and special forces troops to take up positions around the Iraqi seat of government in Baghdad's fortified Green Zone. The move has every appearance of being a coup d'etat, with Mr. Maliki in the role of former dictator Saddam Hussein attempting to rule the nation by force.

The chaos among Iraq's governing elites could hardly come at a more inopportune time. In recent weeks, fighters from the radical Islamic State of Iraq and Syria have overrun large swaths of the country in a drive to create a cross-border Islamic state. They have already captured the city of Mosul in the north as well as two crucial dams that supply much of country's water and electricity, and now they are threatening the semiautonomous Kurdish region around Irbil. Unless the government in Baghdad can rally around a leader capable of persuading all of Iraq's ethnic and sectarian communities to rise up against ISIS, the nation could cease to exist as we know it.

Mr. Maliki is the last person to do that job, however. He is singularly unsuited to forging the kind of broad national unity government needed to check the insurgents' advance and instead has proven to be a polarizing, divisive figure who has alienated Iraq's Sunni minority by arresting and torturing their leaders and marginalizing Iraqi Kurds by refusing them a fair share of the country's oil wealth.

Last week President Barack Obama authorized American airstrikes against ISIS forces closing in on Irbil and airdrops of humanitarian aid to tens of thousands of Yasidis, an ancient Kurdish religious and ethnic group, trapped on a mountain after fleeing the militants' advance. While the airstrikes appear to have allowed the Kurds' Peshmerga militia to regain some of the ground lost to ISIS, their effect may be only to delay the militants' advance. Meanwhile, reports that some Yasidis have taken advantage of the U.S. air campaign to escape into neighboring Syria may also represent only a temporary setback for the insurgents.

Given the gravity of the threats facing the country, U.S. Secretary of State John Kerry has warned Mr. Maliki not to try to obstruct the peaceful transfer of power to a new government headed by Mr. Abadi. But U.S. options for enforcing that message are limited. During his eight years in power, Mr. Maliki consolidated his control over the Iraqi military and police forces and created special operations units loyal to him alone rather than to the government.

If Mr. Maliki does decide to hang tough, his rule conceivably could be challenged by militias of rival Shiite political parties and others who have lost confidence in his ability to lead the country, including even members of his own party such as Mr. Abadi. Even Iran, which backed Mr. Maliki during his rise to power, now believes he has become such a toxic figure that it will be impossible for him to rally the nation's defenses. It cannot welcome a power struggle in Baghdad that devolved into civil war between pro- and anti-Maliki militias, leaving the country ungovernable and easy prey for an ISIS thrust into the capital.

While President Obama warned last week that the limited airstrikes and aid drops begun Friday could last many months, it seems the U.S. has yet to settle on a long-term strategy to keep Iraq from falling apart. Mr. Maliki is clearly an obstacle to uniting the country in its own defense, but despite the frustration that has produced in Washington it's far from obvious that any other Iraqi leader, including Mr. Abadi, would be much better at this point. Members of Iraq's corrupt political elite are notoriously far more obsessed with accumulating power and wealth for themselves than with safeguarding the future of their country.

That's why President Obama is right to view any U.S. intervention there cautiously. Ultimately America can't fix the dysfunctional Iraqi political culture that produced the situation in which the country now finds itself. We can support leaders who are willing to reach out to all Iraq's sectarian and ethnic communities, and give groups like the Kurds, who have long been loyal U.S. allies, access to the weapons and intelligence that allow them to defend themselves. But ultimately it's going to be up to Iraqis to make the hard choices needed to keep their country together. Until they do, the U.S. is better off sticking to the limited role outlined by the administration so far.


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