The attempted assassination of Iraqi Prime Minister Mustafa al-Kadhimi at his Baghdad home Sunday represents a grave escalation in that strife-torn country. The political authorities’ response may determine whether Iraq has a chance to emerge from endless crisis or is set on a path of Lebanonization—de facto rule by armed militias in the service of a foreign state.

No group has claimed responsibility for the three drones launched at Mr. Kadhimi’s residence. But the affiliation of the perpetrators is not in doubt.

Only Iran-supported Shiite militias have the means, motivation and ability to mount an armed drone attack of this type.