It has long been understood that the Spanish socialists shamelessly exploited the March 11, 2004, terrorist attacks in Madrid’s train station for political advantage. They did so with palpable disregard for a frightening fact: The far-reaching geostrategic repercussions of that incident — which vaporized the ruling conservative party’s electoral lead just days before the polling — gave those seeking similar results elsewhere every incentive to engage in violence against other democracies’ electoral processes. But what if the perpetrators were neither Islamofacists, as the winning socialists immediately asserted, nor the Basque terrorist organization known as ETA, as the government of José...