Bronzini joined the Socialist Party in April 1915 and on December 7 he founded the weekly magazine "El Trabajo" ("The Work"), becoming its first director. From 1920 until its demise in 1974, this was the main Socialist newspaper in Buenos Aires Province. Bronzini and other columnists developed a permanent struggle for the Socialist principles of social justice and democracy, with a big compromise towards the public liberties, favouring a suitable and honest handling of the public interests under the scope of the State, and fighting without concessions the advances of the central governments over the municipal autonomy.