The 1966 deposal of President Arturo Illia (of the UCR) by General Juan Carlos Onganía dissolved the Argentine Congress and forced Armendáriz to return to his medical practice. The imminence of new elections in 1972 led him to join fellow former UCR Congressman Raúl Alfonsín in founding the "Movement for Renewal and Change," a center-left faction opposed to the party's longtime leader, Ricardo Balbín, who defeated Alfonsín in their party's primary ahead of the March 1973 elections. Armendáriz's friendship with Alfonsín continued during the turbulent 1970s, when the latter practiced law in defense of victims of the wave of human rights abuses in Argentina, later in the decade. Following Alfonsín's daring and timely opposition of the ill-considered Falklands War in 1982, he became the frontrunner within the UCR on the eve of elections agreed to by the discredited dictatorship, in 1983. Securing the nomination in July, Alfonsín advanced Armendáriz as the UCR candidate for Governor of the Province of Buenos Aires, home to 38% of Argentines.