He returned to UNAM in 1971 to the National School of Law where he attended until 1976, leaving without completing his degree.
Demetrio Vallejo and Heberto Castillo split to form the Mexican Workers' Party (PMT), Rafael Aguilar Talamantes, along with Graco Ramírez, formed the Workers' Socialist Party (PST).
The Workers' Socialist Party was founded as a Marxist political party that believed in the expropriation of financial institutions and many industries, also believing management of state enterprises should be handled by the workers and peasants.
In 1987 the PFCRN allied itself with the National Democratic Front, which supported the candidacy of Cuauhtémoc Cárdenas Solórzano, a former PRI member who had left the party and was running for the presidency supported by a large number of leftist parties and organizations.
After the elections of 1988, Aguilar Talamantes separated from the FDN, and the PFCRN supported many of the policies of the ex-president Carlos Salinas de Gortari.