He was hired as a legal advisor to the CGT, the nation's largest trade union, in 1980. Between 1983 and 1994, he served as senator for the Province of San Luis. Serving this position in 1986, he voted against the Ley de Punto Final that established the suspension of legal proceedings against the perpetrators of illegal detentions, torture and murder during the military dictatorship. Between 1989 and 1993 he was President of the Justicialist caucus in the Argentine Senate. With presidential aspirations of his own, in October 1993 he voted against the government project to amend the National Constitution and allow the reelection of the then-President Carlos Menem, known as the "Pacto de Olivos". This has been linked to the kidnapping of his brother shortly afterwards. He resigned from his seat in December 1994.