A prominent member of Civic Union,[1] he served as Defence Minister during the first years of Julio María Sanguinetti's first presidential term.
Chiarino graduated as a lawyer at the Law Faculty of the University of the Republic (Uruguay), was a militant of the Civic Union of the Catholic party and in the 1930s ran the newspaper "The Public Good" that diffusered ideas of the policy community.
In 1971, along with another PDC splinter group, led by Humberto Ciganda, co-founded the Radical Christian Union (URC) which also was successful in the elections of that year.
Two years later, participate in discussions of the Parque Hotel and the Naval Club Pact, turning points in the transition from Civic-military dictatorship of Uruguay to democracy.
This created a tense atmosphere at the Armed Forces, and Chiarino culminated, after a virtual insubordination of the Army Commander Hugo Medina, facing military citations for justice, with the sanction of the Law on the Expiration of the Punitive Claims of the State, in December 1986, which prevented the continuation of the legal proceedings related to this issue.