Born in Chascomús, Buenos Aires Province, Alfonsín began his studies of law at the National University of La Plata and was a graduate of the University of Buenos Aires. He was affiliated with the Radical Civic Union (UCR), joining the faction of Ricardo Balbín after the party split. He was elected a deputy in the legislature of the Buenos Aires province in 1958, during the presidency of Arturo Frondizi, and a national deputy during the presidency of Arturo Umberto Illia. He opposed both sides of the Dirty War, and several times filed a writ of "Habeas corpus", requesting the freedom of victims of forced disappearances, during the National Reorganization Process. He denounced the crimes of the military dictatorships of other countries and opposed the actions of both sides in the Falklands War as well. He became the leader of the UCR after Balbín's death and was the Radical candidate for the presidency in the 1983 elections, which he won.