How is the discipline of the proletariat’s revolutionary party maintained? How is it tested? How is it reinforced? First, by the class-consciousness of the proletarian vanguard and by its devotion to the revolution, by its tenacity, self-sacrifice and heroism. Second, by its ability to link up, maintain the closest contact, and — if you wish — merge, in certain measure, with the broadest masses of the working people — primarily with the proletariat, but also with the non-proletarian masses of working people. Third, by the correctness of the political leadership exercised by this vanguard, by the correctness of its political strategy and tactics, provided the broad masses have seen, from their own experience, that they are correct.
Vladimir Lenin, “Left-Wing” Communism: an Infantile Disorder