"Getting hold of" can be interpreted broadly. While it’s not unrealistic that the next coalition might be conservative CxU + libertarian FDP + nazi AfD, it’s also very likely that the AfD gets banned until the next election, the responsible organization already has an eye on them. And a government with the AfD would be catastrophic (obviously), but it wouldn’t equal the creation the fourth reich. They would need a 2/3 majority to change/abolish constitutional laws and to change art. 1-20, which ensure human rights and such stuff, they would first need to change/abolish art. 79, which not even CxU and FDP would support. And here’s the fun part: if the AfD actually planned to do that, even without outright stating it, it would be enough to get them banned. The protecting mechanisms are there, the AfD can’t do anything about it and the other parties with coalition potential, even CxU and FDP, wouldn’t pave the way that far for another dictatorship.

So while it’s grim that a Nazi party is that popular, the damage they can possibly do is definitely below 1933.