GenZedong

If specific policies such as halting weapons shipments are under serious discussions then the left should back those policies specifically, not a party or candidate.

This makes sense to me as well, but since Germans can't conceive of a minority government which puts together majority votes on a case-by-case basis, I don't see it happening. Either someone (most likely CDU) agrees to a formal coalition with the AfD or there is a hung legislature and another election in a few months. The third option, a coalition of everyone but the AfD, seems even less likely since the CDU has formally prohibited itself cooperating with Die Linke (AfD as well but aside from the war/Russia question they agree on the important stuff).

I've also seen in Canada how the "anti-establishment" parties end up governing at the provincial level. Of course being against everything makes it hard to be for specific things to put into law, so these governments give handouts to their capitalist patrons and drinking buddies while spending the rest of the time complaining that they can't get anything done because everyone else is against them. I can see an AfD state government going in much the same way.