Part-time class struggle. The fringes of the Polish inter-war communist movement This article is to examine some obscure forms of involvement in the Polish inter-war communist movement: the Communist Party of Poland and its subordinate organisations. The author focuses on the fringes of the movement, a borderland between a revolutionary, subversive organisation and the “outside world”. There is a particular emphasis on the perspective of men and women operating in this borderland. The protagonists of the paper are communism “sympathisers” — those who did not belong to the organisation, but identified with its ideas and provided support to it, as well as members of the organisation whose ties to the movement, however, were loose or who gradually moved away from active involvement. In contrast to the dominant depictions focused on public figures, intellectuals, and artists, the author deals with “ordinary” plebeians or white-collar workers. The article provides answers to some important questions about belonging to the communist formation, but also about involvement in the political sphere in general. It reveals tensions between the ideological self-identification of individuals and its recognition by the reference group, as well as the patterns and limits of personal agency in a clandestine political movement. In addition, the author considers the role of both ideological factors as well as “biographical accessibility” (determinants such as health or family conditionings) in individuals’ definition of their role in the political sphere. The source material for the article primarly consists of ego- documents from archival personal files, allowing for a reflection on strategies of favourable self-presentation and mechanisms of party self-criticism.