This work has as its main character Ernani do Amaral Peixoto, one of the most detached politicians in Rio de Janeiro between 1937 and 1975. Analyzing the available letters of his personal files and the statements from politicians that somehow were related to him, we have identified the amaralismo as a predominant policy culture in Rio de Janeiro State between 1937 and 1955 and the actions that have led the construction and consolidation of Ernarni do Amaral Peixoto as a policy leadership at this period. This work intent to analyze how Amaral Peixoto, a foreign in the state policy until 1937, was able to form a politic group in the course of the Estado Novo and keep his supremacy in Rio de Janeiro, even after the end of this political system. Although his importance to the state and national policy, the scarcity of works about Rio de Janeiro State after Getúlio Vargas government (1930-1945) has contributed to the fact of his trajectory has been unexplored by historians. The Commander, as he was known by his position on the Brazilian Navy, had decisive participation in the fluminense policy and performed important rolls also in national ambit, participating actively of the process that led the country to democratization at 1945.