Talk of succession is in the air. After 18 years, Angela Merkel is stepping down as chairwoman of the Christian Democratic Union, Germany’s main ruling party since 2005. The party’s conference meets this week in Hamburg to decide her replacement. But whoever follows Ms. Merkel — for many, Europe’s de facto leader — will inherit a fractious party and, if Ms. Merkel is unwilling or unable to see out her chancellorship through to 2021, a fragmented country.

The stability (and even monotony) associated with German politics under Ms. Merkel appears to be coming to an end. Her looming retirement marks a deepening crisis of the German political system that threatens not just the future of the country, but of the European Union.

Explanations for this shake-up often begin and end with Ms. Merkel. Her handling of the so-called refugee crisis and her downbeat, aloof style alienated large chunks of the electorate . The gradual weakening of the centrist parties has in turn fed polarization and the fragmentation of the electorate.

But Ms. Merkel, for all her power and influence, is just one politician. Germany’s new political crisis runs much deeper. It stems from an economic system that has resulted in stagnant wages and insecure jobs. The erosion of Germany’s postwar settlement — a strong welfare state, full-time employment, the opportunity to move up in the world — has created a populace open to messages and movements previously banished to the fringes.