[yorwba]

Could you give me a source for the claim that the Wahlprogramm is legally binding?

I was always under the impression that it was more a declaration of intention, to be fulfilled on a best-effort basis. Otherwise, how would coalitions between parties work, if they can't deviate from their program?

Even if it were legally binding, that doesn't preclude making decisions on topics that weren't even covered. In those cases, you can only trust that the party has a consistent ideology they will follow. The AfD seems to be judged more for their ideological tendencies than for any demands they have formally elevated to the party line.

[pluma]

I'm sure the voters of 1998 would love to have seen the Greens be sued for their support of militarism, or the SPD for their neoliberal labour reforms. But alas there were merely a few protests.

If the Wahlprogramm were legally binding, there would have been plenty of opportunities to sue.

For the record: the reason the Verfassungsschutz might tear into a party is usually because the party harbors anti-constitutional ideas or associates itself with criminal organisations, e.g. the NPD with its neo-nazis or the Left with antifa.