[citation needed] El Mercurio received funds from the CIA in the early 1970s to undermine the Socialist government of Salvador Allende, acting as a mouthpiece for anti-Allende propaganda.

[1] Declassified documents that detail US interventions in Chile revealed the paper's role,[2] and the extent of the paper's cooperation with the CIA: "Throughout the 1960s, the CIA poured funds into Chile's largest—and staunchly right-wing—newspaper, El Mercurio, putting reporters and editors on the payroll, writing articles and columns for placement and providing additional funds for operating expenses.

Throughout Allende's aborted tenure, the paper continued an unyielding campaign, running countless virulent, inflammatory articles and editorials exhorting opposition against—and at times even calling for the overthrow of—the Popular Unity government. "

"[3] (p. 93) The paper played "a significant role in setting the stage for the military coup" which took place on 11 September 1973, bringing General Augusto Pinochet to power.

It mobilised opponents of President Salvador Allende and the gremialismo movement to be active in destabilisation from the street, while also advocating the neoliberal policies of the yet-to-come Chicago Boys.