The Arab Spring began in Tunisia, and it’s lurching toward the brink again just weeks after the Egyptian army overthrew the Muslim Brotherhood government. Last week an assassin took out left-wing opposition leader Mohammed Brahmi with a 9mm pistol. Ballistics reports indicate the killer used the exact same weapon to murder another opposition leader, Chokri Belaid, last winter. And this week Al Qaeda-linked terrorists dug in on Mount Chambi killed at least eight Tunisian soldiers. Ennahda, the local branch of the Muslim Brotherhood, is taking the heat. While they aren’t being fingered as directly responsible, they’re being blamed all the...