The mid-right said they wouldn’t work with them, but as we have seen that means absolutely nothing. I wouldn’t be surprised if the SDP CDU broke that and started working with AfD.

I’m also very worried about that, but it’s another point of difference - there were historically enormous protests (tens to hundreds of thousands per city, well over a million total, more than a percent of Germany’s total population) several times recently because CDU looked like it was slightly cooperating with them with an informal and unbinding agreement about immigration. These protests had the support of the churches, the sports leagues. Various senior government figures support outright banning the AfD. It would not be as easy for them as in the USA, where everyone immediately capitulates.