No social fascism theory, No further KPD split. As Brüning's austerity policies radicalise in 1931, so does the SPD and unions, with both parties putting aside their controversies with the KPD for the Moment to form a Popular Front against wage Cuts, layoffs, unemployment benefit cuts, and worse. For worse is certain to loom: with the Red Threat much more real than OTL, even more bourgeois, industrialist and Junker circles will openly favour Military dictatorship and)or collusion with the Nazis. A coalition between right-liberal, conservative and Nazi Parties, Like OTL"s in Brunswick or Thuringia, has dozens or better hundreds of striking workers shot, imprisoned and tortured, or similar, so the working class is more scared and aware of what awaits them.
The Zentrum splits, its Right and Left Wings Formung separate Parties and joining opposing Camps.
All this gives Hindenburg a Heart Attack and He Kicks the bucket in 1932 before the parliamentary elections. Hitler and a moderate social democrat like Wels Duke it Out in the second round, with Wels carrying a narrow Victory.
Both Camps try their ugliest to tamper with the Reichstag elections of 1932, but neither Side gains a majority (there are still centrist splinters around). Wels appoints a social democrat as chancellor. A Military Coup, supported by SA and Stahlhelm, breaks Out. Red and loyalist-republican militia form to defend the legitimate government. Civil war in Germany.
In 1933, some months into it, the Republicans (yes, the parallel with Spain should be obvious by now) look like they're losing ground. The international community is mostly standing by; Britain, France and the US do not offer to postpone reparation payments and even hamper the official government's abilities to obtain loans and buy what they need etc. on international markets when they default on the reparation payments (which they must); Italy and Austria, where a similar civil war rages, only with the roles reversed: the official government is Right-wing, and socialist rebels hold Vienna and its environs, are openly siding with the German putschists. The Republican government, in this situation, turns to Moscow as their only hope (for reinforcements as well as all sorts of civil and military imports). Stalin demands that a communist be made chancellor, and the government restructured to allow for greater KPD influence. Wels yields.