In 1917 he acceded for the first time to the Deliberative Council in representation of the Socialist Party, being reelected for 1918/19. The electoral success of November 1919 allowed the revolutionary fact of consecrate Bronzini as Socialist Mayor in a city like Mar del Plata, a safe haven to the summer-visiting Argentine upper class and its local sympathizers. He is considered thus one of the first socialist Mayors of the Americas. That first period (1920–21) was briefly interrupted by an arbitrary intervention of the provincial government, who had to restore him in office by judicial ruling. For the period 1922–23, Socialist councilman Rufino Inda was elected Mayor. Bronzini returned to office for the period 1924–25, as councilman in 1926–27, and again as Mayor for 1928–29. This period was also interrupted by another illegal intervention in September 1929, just 60 days after his electoral success, in order to prevent a new socialist mandate.