With Bârlădeanu, Grigore Preoteasa, Gheorghe Rădulescu, Constanța Crăciun, and others, Constantinescu founded the anti-fascist "Frontul Studențesc Democrat" (FSD, the Students' Democratic Front) in 1935. The group was, in effect, an outlet of the Communist Party — its entire leadership continued to carry party work throughout the FSD's existence. The following year, as the UTC was dissolved, Constantinescu was among the few of its members to continue political activity in PCR ranks. In 1938, during the National Renaissance Front regime established by King Carol II, the Communist Party ordered him to reestablish the UTC. He was among the few intellectuals at the forefront of party activities.