The petit bourgeoisie assumed proletarian leadership and then betrayed it.

Evidence

Within those same centuries, then, though it was possible to trace the maturation of the bourgeoisie and the working classes, it was also necessary to recognize the transformation of the petit bourgeoisie. It was necessary because this strata had presumed the leadership of the proletarian movement and then betrayed it. — Cedric J. Robinson, Black Marxism_ The Making of the Black…, 1321