Upon the end of the conflict, he decided to, in his own words: In December 1904, Frugoni wrote his Profesión de fe socialista ("Socialist Testimonial") - which was partly published in the newspaper El Día.
Elected deputy in 1934, he had opposed the dictatorship enforced by the legislature, and, upon the swearing in of Terra, declared: He walked out of the Parliament to the PS headquarters as the former was stormed by police forces.
In 1942, Frugoni was named Uruguay's Envoy Extraordinary and Minister Plenipotentiary to the Soviet Union by President Juan José de Amézaga.
In La Esfinge Roja (1948), the book containing his experiences, he wrote: In January 1963, he left the PS over internal disagreements, and created Movimiento Socialista, with which he ran in the elections of 1966.
In 1966, he authored an Open Letter to the Socialists; among other things, it stated that "an electoral campaign is nowadays an economical adventure", and showed Frugoni's willingness to contribute his personal wealth.