It was founded in 1963 by the labor leader Juan Lechín Oquendo and by Mario Torres Calleja and Edwin Moller in lesser roles.
[1] The PRIN combined the left wing of the MNR and former members of the Revolutionary Workers' Party (POR).
It was also weakened because Juan Lechín was deported to Paraguay by the military junta, he spent many years in exile between 1965 and 1978.
[3] For the 1979 elections, the PRIN was the component of the Democratic and Popular Union, with the MNRI's Hernán Siles Zuazo as the coalition's presidential candidate.
[3] Following the end of military rule in 1979, a member of the PRIN, Lidia Gueiler Tejada, was appointed interim president.