“We will always remember her most profound love for the children and her solidarity with those who suffered because of the disappearance of their loved ones,” President Andrés Manuel López Obrador of Mexico wrote on Twitter.
Mrs. Ibarra became a senator, a political adviser and the first woman to run for president of Mexico, in 1982 and 1988, as the candidate of what was then the Revolutionary Party of the Workers.
Her missing son, Jesús Piedra Ibarra, a medical student and leftist who was accused of belonging to a guerrilla group and of killing a police officer, disappeared in April 1975. It later came to light that he had been arrested, apparently by government authorities, and beaten, tortured and taken to a military camp in Mexico City. He was last reported alive by the news media in 1984. His body was never found.
For two years, Mrs. Ibarra trekked around Mexico looking for him. She visited police chiefs, politicians and even the president of Mexico at the time, Luis Echeverría Álvarez, confronting him on several occasions to demand that the government return her son.