There is no singular solution to Iraq's vexing crisis. But amidst the uncertainty and chaos, this much is clear: If Iraq is to have any hope of navigating out of its current mess, Prime Minister Nuri al-Maliki must step aside. On that point, even the most unlikely of allies have reached a common consensus. The United States, Iran, Sunni and Shia leaders have all urged Mr. al-Maliki to make way for a new leader – Haider al-Ibadi – to form a government. The trouble is, Mr. al-Maliki doesn't seem to care.

His refusal to step down is grounded in the delusion that he is the man who can somehow restore his country to relative calm. He is wrong. During his two-term tenure as Iraq's prime minister, he has shown himself totally incapable of addressing what lies at the root of Iraq's problems. Instead of bridging the country's divisions, he has steadily exacerbated them.

He has consistently and spectacularly failed to incorporate minority Sunnis into Iraq's democratic political process, preferring to promote his fellow Shiites to positions of power. The Sunnis' simmering sense of disenfranchisement has paved the way for the Islamic State of Iraq and the Levant to make alarming territorial gains, inflicting its twisted brand of Islam on minority sects by presenting them with a brutal ultimatum: Convert to Islam or die. Instead of supporting Iraq's central government, many Sunni tribal leaders are so disaffected that they are now fighting alongside ISIL.

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Iraq doesn't have to look this way. Sunni leaders have previously shown themselves quite capable of moderation, working within the political process in the interests of democracy and peace. They served as leaders in the Awakening movement, which restored order in large parts of the country, diluted al-Qaeda's influence and eased sectarian tensions before the American withdrawal. Mr. al-Maliki saw the Awakening movement as a threat, and stopped paying its members' salaries. Now Iraq is contending with al-Qaeda's virulent offshoot.

Winning back Sunni leaders' trust will be no small feat, but it is not impossible. Sunni leaders have no natural allegiance to ISIL, who are religious fanatics, and viewed by many Sunnis as a foreign force. Many consider the current alliance with ISIL a temporary one – to be severed once Mr. al-Maliki is gone. His insistence on clinging to power sabotages any hope Mr. al-Ibadi has of pulling Iraq back from the abyss. It's time for him to go.