One of the strongest Trotskyist opponents of the Tristán Marof, Guillermo Lora (leader of the POR), admitted that the PSOB "was in its time a party with a large membership and succeeded in achieving national proportions."
[3] During the administration of President Enrique Peñaranda del Castillo (1940–1943) the Party supported this conservative regime.
In 1943 after Gualberto Villarroel López’s revolution, the Workers Socialist Party of Bolivia was strongly persecuted and did not succeed in electing any members of Constituent Assembly in 1944.
It ran candidates on 5 January 1947 election for National Congress, with Carlos Salazar and Alipio Valencia Vega.
The principal reason for this was the fact that Tristán Marof accepted the post of private secretary to President Enrique Hertzog Garaizabal, a representative of the traditional ruling oligarchy.