After the return to democracy in Argentina in 1983, he was named Secretary of Culture of the city of Buenos Aires.

He ran unsuccessfully for the 1988 presidential nomination in the Radical Civic Union primaries, but later became a Peronist and was elected to the Argentine Senate for the city of Buenos Aires in 1998.

[2] President Carlos Menem appointed O'Donnell Ambassador to Bolivia and Paraguay, as well as Secretary of Culture.

[3] He is currently engaged on the diffusion of Argentine historical knowledge, being part of the "neorevisionist" school which contests the official reading of history imposed in Argentina (democracy being restored only in 1983), and hosted the television show Historia confidencial (Confidential History) with fellow historians José Ignacio García Hamilton and Felipe Pigna.

[citation needed] He received the "Isabel la Católica" ("Isabella the Catholic") order from the Spanish King Juan Carlos I of Spain, and the "Palmas Académicas" ("Academic palms") in France.