At least we "psephologists" should be aware, that the NSDAP had been exploding in regional elections (from 0-1%) already months before Black Friday.
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It would be a misconception to think that before Black Friday it was all roses and flowers in the Weimar Republic.
Rural areas and peasants in particular had been in a structural crisis for decades. They blamed increasing free trade and taxes for their economic difficulties and felt that they had no political representation in the established parties. (SPD, DDP and DVP were considered to represent city/industry-interests, DNVP was considered to represent East-Elbian squires.)
Still I think that the new world-wide economic crisis that went far beyond agriculture heavily exacerbated things.
But the NSDAP was in protestantic Germany (and Austria) a party of the bourgeoisie in small/medium-sized towns&markets, in Germany's (by BISMARCK's KulturKampf endangered) catholic minority even one of the secularized cities. In Austria they did, as the studies of D.HÄNISCH demonstrate, electorally terribly in areas with a high PerCentage of peasants (even those of the german-nat. LandBund/LB).
It depends. The strongest results for the NSDAP in 1928 came from areas of agricultural unrest in parts of Schleswig-Holstein, although the independent farmers of Dithmarschen probably don't fit the peasant stereotype.
Later many of the strongholds of the NSDAP were in rural and small-town areas that had experienced stagnation, emigration and and increasing marginalization during Germany's industrialization. The country's East, but also e.g. rural Northern and Central Hesse and the vast border areas between Franconia and Württemberg (The district of Rothenburg o.d.T. was the NSDAP's absolute stronghold, the villages even more than the medieval "city").
I was imprecise regarding the NSDAP being a party of the peasantry. More than anything else it became to represent the "old" downwardly-mobile middle-classes: Small-town civil servants, craftsmen, traders, independent farmers.
The point that I wanted to make originally is that the NSDAP had some (limited) success even before
Black Friday, because even before Black Friday it wasn't all roses and flowers. But without Black Friday it would probably not have come anywhere near to its actual success.