Germany's Bundesamt für Verfassungsschutz, the Federal Office for the Protection of the Constitution, is constantly on the lookout for potential threats to Germany's democratic constitutional system, and it has wide-ranging powers when it finds them.

"This agency has the power — and not only to do surveillance on fringe groups, domestic terrorist threats, but also to keep an eye on any political institution, like a political party," explains Melanie Amann of the German newsmagazine Der Spiegel and the author of a book about the AfD. "Like if their program becomes more radical or if they notice that a political party, maybe that's even sitting in the parliament, goes into a direction that might be harmful to our political system."

The agency has wrapped up a two-year investigation into Germany's largest right-wing opposition party, the Alternative for Germany, or AfD, and is expected to announce soon that it will place the entire party under surveillance for posing a threat to Germany's political system and violating the constitution. The unprecedented move would mean that all AfD lawmakers, including several dozen in Germany's parliament, would be put under state surveillance.