He was minister of Education under Franco (1951-1955) but he drifted apart from the Francoist State since 1956 and, adopting a Christian Democrat position, steadily started to promote a quiet transition to democracy, especially through Cuadernos para el Diálogo magazine.
Ruiz-Giménez was son of Joaquín Ruiz Jiménez, Liberal politician who was minister twice under Alfonso XIII and mayor of Madrid.
After the Civil War broke out he was imprisoned several times, but finally released he sought asylum at the Panamanian embassy, and thus he was evacuated to Marseilles via Valencia.
He collaborated actively in the redaction of the Fuero de los Españoles, i.e. a sort of bill of rights promulgated by Franco in 1945.
Cuadernos para el Diálogo was the most dissident option within the legal narrow framework of freedom of speech allowed during the last decades of Franco's reign.