During the early stages of the EU crisis, most threats to the survival of the Continental bloc came from its periphery. Back then the prevailing fear was that financial disaster in a southern member state -- a default in Greece or Portugal, for example -- could precipitate the eurozone's collapse, hurting northern nations such as Germany and the Netherlands in the process. Though the possibility still exists, a sort of inverse threat has emerged. Today, the steady rise of anti-establishment and Euroskeptic sentiments in Northern Europe, as exemplified in Austria and Germany, threatens the Continent's south....