“It shows you how difficult it is in a democracy … to define very clearly what is beyond the border of what’s acceptable,” Jan Techau, the Berlin-based director of the German Marshall Fund’s Europe program, told me. “It brings up the question, to what extent can an open society actually defend itself against its enemies?”

Germany’s history is clearly reflected in its political system: After World War II, its constitution and institutions were designed with the underlying goal of preventing the rise of another Nazi regime. The domestic intelligence agency, for example, is called the Federal Office for the Protection of the Constitution (or Bundesamt für Verfassungsschutz), and is just one of many particular aspects of German democracy—some codified in law or in the constitution, others unwritten rules of political engagement—aimed at protecting democracy and combatting extremism, particularly on the right.

“The basic idea behind [the German political system] is that certain boundaries must be drawn within democracy, that should make it impossible for an antidemocratic force to take over power,” says Steffen Kailitz, a professor of political science at the Hannah Arendt Institute for the Research on Totalitarianism in Dresden. “Whether that is realistic is another question."

Under the German constitution, extremist groups can be not only monitored but even banned (something that has happened to political parties only twice, most recently in the 1950s). German law makes it a crime to deny the Holocaust and to display Nazi imagery or the Hitler salute. Restrictions on hate speech, which under German law can range from incitement of violence to certain statements about specific religions or religious organizations, are stronger here than in many other Western countries, particularly since the introduction last year of a law governing online speech. These institutions are far from perfect: Haldenwang’s predecessor at the Verfassungsschutz was fired last fall after questioning the authenticity of videos from the far-right demonstrations in Chemnitz last summer, and the agency has been criticized for having a blind spot when it comes to far-right extremism. But they exist with the goal of protecting German democracy, and such limits on Holocaust denial or Nazi imagery are there for what many politicians say is good reason.

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“These limits have arisen from German history. Whether that makes sense or not, you can discuss—but that’s the way things are,” Stefan Liebich, a lawmaker from the Left party, told me.

The AfD is perhaps the biggest test yet for these boundaries. Though the party is hardly the first far-right movement to try to compete in Germany’s postwar political ecosystem, it’s by leaps and bounds the most successful one: More than five million people supported the AfD in the 2017 federal elections, earning it 12.6 percent of the vote nationally and more than 90 seats in the German Bundestag. And as of October, the party is represented in all 16 of Germany’s state legislatures.