Following an episode of liberalization in the late 1960s, Ceaușescu again adopted a hard line, and imposed the "July Theses", radicalizing the party's rule by intensifying the spreading of Marxist-Leninist thought in Romanian society and at the same time consolidating Ceaușescu's grip on power.
Over the years, the PCR massively and artificially increased in size, becoming entirely submitted to Ceaușescu's will.
The PCR was a minor and illegal grouping for much of the interwar period, and submitted to direct Comintern control.
The onset of the Great Depression in Romania, and the series of strikes infiltrated (and sometimes provoked) by the interior wing signified relative successes (see Lupeni Strike of 1929), but gains were not capitalized—as lack of ideological appeal and suspicion of Stalinist directives remained notable factors.
In parallel, its leadership suffered changes that were meant to place it under an ethnic Romanian and working class leadership—the emergence of a Stalin-backed group around Gheorghe Gheorghiu-Dej before and after the large-scale Grivița Strikes.
During the 1930s, most of its activists were imprisoned or took refuge in the Soviet Union, which led to the creation of separate and competing factions until the 1950s.
The Communist Party emerged as a powerful actor on the Romanian political scene in August 1944, when it became involved in the royal coup that toppled the pro-Nazi government of Ion Antonescu.