The new contours of Bolshevik politics determined the tactics available not only to the Left but to all factions that would emerge to challenge the CC majority after Lenin’s passing. Crucially, the decision to open the party’s doors to a new cohort of rank-and-file communists introduced a new variable to internal politics. The Lenin enrolment had transformed primary party organisations from isolated, demoralised groups of communists to mass institutions tightly woven into the fabric of factory life. Both oppositionists and the centre tried to manoeuvre this new dynamic to their advantage. The following pages will examine this process as it unfolded during the bitter factional struggles against the so-called New and United Oppositions, the last major challenges to the NEP consensus.