The POR was founded in December 1935 at a congress in Córdoba, Argentina, called by Gustavo Navarro and other Bolivian radicals who were in exile because of the Chaco War.
Under the advice of José Aguirre Gainsborg, the leaders of the new POR affiliated with Leon Trotsky's International Left Opposition.
Following the "Bolivian National Revolution," the MNR took over the government, but the populist party failed to enact major social reforms because of pressure from international agencies.
The faction of the POR led by Guillermo Lora continued its activity in the COB and FSTMB during the 1960s and 1970s, when the country was ruled by a series of short-lived military juntas.
Lora's POR worked closely with FSTMB president Juan Lechín during these years, when the labor movement largely operated clandestinely.
The wing of the POR led by González Moscoso, which remained the official affiliate of the Trotskyist Fourth International, turned to the idea of armed insurrection against the government.
Lora's POR continues to exist to the present day, though it has been eclipsed by other radical parties such as Evo Morales' Movement toward Socialism (MAS).