Founded in 1921 as the Portuguese Section of the Communist International, has its major influence among the working class and played a major role in the opposition to the Estado Novo regime, being brutally repressed in the process. After being one of the most influential parties in the years that followed the Carnation Revolution, it lost most of its power base after the fall of the Eastern Bloc, but still enjoys popularity in vast sectors of Portuguese society, particularly in the rural areas of Alentejo and Ribatejo and also in the heavily industrialized areas around Lisbon and Setúbal. It also has a major influence among the biggest Portuguese labour union – General Confederation of the Portuguese Workers (CGTP). Its historical leader was Álvaro Cunhal.
