Fernando de la Rúa was the son of Eleonora Bruno and Antonio De la Rúa; he was born in the city of Córdoba and attended the local Military Lyceum before entering the National University of Córdoba, from which he graduated with a law degree at the age of 21. He married a Buenos Aires socialite, Inés Pertiné, in 1970; they had three children, including Antonio de la Rúa. De la Rúa became involved in politics at a young age; he entered public service in 1963 as an advisor to President Arturo Illia's minister
He was elected senator in the March 1973 general elections, defeating the Peronist Marcelo Sánchez Sorondo. He was the only politician from the Radical Civic Union (UCR) who could defeat the Peronist candidate in his administrative division. The elected president Héctor José Cámpora and his vice president resigned a few months later, leading to the call to new elections. Ricardo Balbín ran for president in the September general elections, with De la Rúa as his running mate for the post of vice president. The UCR was defeated by Juan Perón in a landslide. De la Rúa was removed from the Congress during the 1976 Argentine coup d'état. He left politics and worked as a lawyer for the firm Bunge y Born.
The National Reorganization Process ended in 1983. De la Rúa intended to run for president but lost in the primary elections of the UCR to Raúl Alfonsín, who was elected in the general election. De la Rúa ran for the post of senator instead, defeating the Peronist Carlos Ruckauf. He ran for re-election as senator in 1989 but, despite his electoral victory, the electoral college voted for the Peronist Eduardo Vaca. De la Rúa was elected deputy in 1991 and returned to the senate in 1993. President Carlos Menem, elected in 1989, wanted to amend the constitution to allow him to run for re-election in 1995, which was opposed by the UCR. Alfonsín signed the Pact of Olivos with Menem, negotiating terms to support the proposal. De la Rúa led the opposition to the pact within the UCR, but Alfonsín prevailed in the internal dispute. This damaged the relationship between the two leaders, but helped the party to retain a number of radicals who were against the pact. De la Rúa could not prevent the 1994 amendment of the Argentine Constitution. As a result, Menem was re-elected in 1995. The UCR finished third in the elections for the first time, being surpassed by the Frepaso, a new party composed by former Peronists.