After studying Law and Economy at the University of Cluj (1930–1934), he engaged in local politics with the PNR's direct successor, the National Peasants' Party (PNŢ), and worked as a journalist; he wrote for "România Nouă", edited by Zaharia Boilă, "Mesajul" (Zalău), "Unirea" (Blaj). He became the private secretary of Iuliu Maniu, the leader of the PNR and PNŢ, who had been a leading actor factor in Transylvania's union with Romania (1918), and as head of the Transylvania Directory Council. Coposu wrote in detail about this experience in his ”secret diary”, discovered after the collapse of communism and published in 2014.