The two most likely outcomes are, depending on when and what your POD is, a Communist Räterepublik or an authoritarian presidential semi-dictatorship. THe earlierm, the more likely the former, the later, the more likely the latter. By 1933, the Communists were largely a spent force and even many moderates would welcome an authioritarian state if it promised to restore order. In the early 20s, it was touch and go.