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," said Melanie Amann of the German newsmagazine Der Spiegel and the author of a book about the Alternative for Germany, or 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 the Alternative for Germany, the country's largest right-wing opposition party, 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.

The driving force behind the creation of the Verfassungsschutz agency and its surveillance powers was the American-led Allied forces, who, after World War II, helped write a new German Constitution with an eye toward preventing the return of Nazi ideology. That's why the first article of the constitution guarantees the right to human dignity — an article that the agencydetermined a far-right branch of the AfD violated. It placed that group, known as der Flügel("The Wing"), under surveillance nearly a year ago.

Amann said the agency has identified instances of AfD politicians denigrating Muslim migrants to Germany. "They were all treated as potential terrorists," she said. "They were dehumanized in the speeches. They were compared to animals. The [agency] report made it quite clear that these people had crossed a line."

Some AfD politicians have also trivialized Germany's Nazi past. Speaking at an AfD event in 2017, the leader of the Flügel wing, Bjorn Höcke, called the Holocaust Memorial in Berlin a "monument of shame." A year later, AfD parliamentary leader Alexander Gauland likened Germany's Nazi era to "a speck of bird s*** in more than 1,000 years of successful German history."

"If you look at how the AfD has been behaving for some time now, it's clear it's acting against our democracy and our constitution," said Social Democrat parliamentarian Thomas Hitschler, a member of the parliamentary committee that reviews Germany's intelligence agencies. He said the Verfassungsschutz agency has spent two years gathering evidence to inform the decision that is expected to put the entire AfD under watch.

But AfD politician Georg Pazderski claims the process is political. The agency is run by Chancellor Angela Merkel's government, staffed with members of her own conservative Christian Democratic Union party. Pazderski said the CDU is worried about how fast the AfD has become a presence in Germany's parliament; the party now has 88 members of 709 in the Bundestag, more than 12% representation.

"If you have an opposition party which is very successful within a very short time, we become a danger for the ruling parties," Pazderski said, "especially for the conservative CDU. And this is a reason why they are trying to stigmatize us and to really put us in the Nazi corner and also to spread strong rumors."

Hitschler insists the process is not political and the agency's findings must withstand tough legal scrutiny.

"Its decision must be so watertight legally that it will stand up in the courts," he said. "The AfD has legal recourse to contest the decision, and the agency isn't about to lose face in court with a poor case."

The AfD is already preparing for the decision. This week, the party published a position paper that represents a U-turn in how it sees immigrants, insisting that it is a party for all Germans, even naturalized citizens.

AfD politician Jens Maier, already under surveillance for being part of the Flügel, told NPR by email that last year's decision to put his section of the party under surveillance has had real consequences.

"A lot of members fear for their civil reputation or even their jobs, especially if they are employed in public service," he wrote. "This is clearly an unfair method to lower the election results of the AfD." Germany's federal elections are scheduled for September.

Der Spiegel's Amann says tightened surveillance on the AfD will affect civil servants such as police officers and military personnel, who may cancel their membership out of fear of losing their jobs.

While the Verfassungsschutz agency is able to tap phones and use informants to gather information on whomever it monitors, Maier said he hasn't noticed the surveillance. But he said it has changed the way he and his associates communicate.

"We don't talk about confidential topics on the phone or online anymore and people from the outside contacting us do so with care now, knowing that somebody is possibly listening," he wrote.

When Germany announces the AfD is under surveillance, Pazderski said it can expect an immediate lawsuit challenging the decision. And that, he said, may take years to resolve.

Esme Nicholson contributed to this report from Berlin.

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