Miquilena began his political career with the Venezuelan Communist Party (PCV) in the 1940s as Secretary General of the Union of Bus Drivers (Spanish: "Sindicato de Autobuseros"), allied with President Isaías Medina Angarita. He remained with the PCV for the next four years. Later, he became a firm opponent of president Rómulo Betancourt (first presidency 1945-1948). In 1945, he broke with the PCV over their support of Betancourt and formed his own political party, the Revolutionary Party of the Proletariat (PRP). The PRP was short-lived, lasting from the overthrow of the Gallegos government (in office February 1948-November 1948) until the rise of Marcos Pérez Jiménez.