The Third Period was one of lost opportunities, when considering that both the SPD and the Nazis were not really united.
Instead of vulgar Popular Fronts or completely hopeless United Fronts (militant hostility of the SPD leadership and middle ranks towards the KPD to the point of violence on the streets), a pro-Soviet Communitarian Populist Front emerged in Weimar Germany to take advantage of the deteriorating economic and political situation. This front included the KPD and the SPD splinter party, the SAPD (Socialist Workers Party of Germany).
Programmatically speaking, these CPFists aimed for these basic political demands:
1) Combining legislative and executive power, perhaps expanding the jury system to the point of replacing judges altogether;
2) Eliminating any formal or de facto disqualifications re. the political process (political decision-making and holding public office) due to non-ownership of non-possessive property or, more generally, of wealth;
3) Formation of separate and sovereign socioeconomic governments for matters other than high politics, security politics, and all other related state politics - but directly representative of ordinary people instead of being organized on a Corporatist basis;
4) All public officials to be recallable and on average workers' wages;
5) Full freedom of class-strugglist assembly and association for people of the dispossessed classes, even within the military, free especially from anti-employment reprisals, police interference such as from agents provocateurs, and formal political disenfranchisement;
6) Expansion of the ability to bear arms and to general self-defense towards enabling the formation of people’s militias based on free training, especially in connection with class-strugglist association, and also free from police interference such as from agents provocateurs;
7) Suppression of state debts and the general repudiation of Versailles;
8) Full nationalization of the financial system and explicitly confiscatory, despotic measures against all capital flight of wealth, investment strikes, and other elitist economic blackmail, whether the related wealth belongs to economic rebels on the domestic front or to foreign profiteers.
However, like the original Communitarian Populist Front that was the Paris Commune, some socially conservative measures were raised, such as strict measures against gambling. Child welfare and maternal support aimed at boosting the German population was raised, too.
In light of #7 and #8 above, however, they were not afraid to make appeals to nationalism and Pan-Nationalism (since capital flight and investment strikes aren't "patriotic"). Enter the nationalist element of the Communitarian Populist Front
, the likes of: nationalist splinters from the KPD (Heinrich Laufenberg and Fritz Wolffheim), the Group of Social Revolutionary Nationalists (Karl Otto Paetel), unorganized people like Ernst Niekisch, and whatever working-class elements supported the Nazis - who then smartened up to realize Hitler's Long Knives contempt for "that program" (true in real life, the official NSDAP was to Hitler what the SPD's Erfurt Program was to Friedrich Ebert).
The Nazis themselves were reduced to a rump petit-bourgeois party because of the departure of whatever working-class support they had.