The Seguro Obrero Massacre took place on 5 September 1938, in the midst of a heated three-way election campaign between the liberal-conservative Gustavo Ross Santa María, the radical Popular Front's Pedro Aguirre Cerda, and the newly formed Popular Alliance candidate, Carlos Ibáñez del Campo.
On September 5, 1938, the Seguro Obrero Massacre occurred during a three-way election campaign featuring liberal-conservative Gustavo Ross Santa María, radical Popular Front's Pedro Aguirre Cerda, and the newly formed Popular Alliance candidate Carlos Ibáñez del Campo.