[1][2] He became affiliated with the Integration and Development Movement (MID), a pro-industry political party, and on March 2, 1972, was hired as an advisor to Ernestina Herrera de Noble, the director and majority owner of Clarín, the most widely circulated newspaper in the Hispanic world.

He nevertheless maintained cordial relations with the runner-up of that campaign, Justicialist Party Governor Eduardo Duhalde, who was appointed President by the Argentine Congress following the December 2001 riots in Argentina that led to the resignation of his predecessor, Fernando De la Rua.

Magnetto was able to parlay this understanding into Duhalde's support for a "Law of Preservation of Cultural Patrimony," which limited foreign ownership of local media to 30%, thereby protecting the Clarín Group's core businesses.

[6] Magnetto had worsening health problems, chief among them esophageal cancer in early 2007, which for a time led to speculation as to his continuity as CEO of the Clarín group, as well as to a possible dispute over his 30% share in the company.

[8] Former Argentine President Néstor Kirchner alleged that, during the 2008 Argentine government conflict with the agricultural sector, Magnetto offered a supportive spin on the administration's case for higher export tariffs, in exchange for an amenable treatment of the media group's acquisition of a significant stake in Telecom Argentina (a potential anti-trust law violation); the hitherto cordial relations between Kirchnerism and the Clarín Group soured during the conflict.