Democratic centralism, a hallmark of Leninist party organizations, has played a formative role in the history of the Chinese Communist Party (CCP). Yet despite being hailed as an “inviolable” and “unchanging” Party principle, understandings of democratic centralism have shifted dramatically over the century of its existence. This study traces the long arc of the concept's evolution across successive Party Constitutions, focusing on three critical historical junctures: the Sixth Party Congress, which formally adopted democratic centralism into its Constitution as an organizational principle; the Seventh Party Congress, which adopted rectification as the Party's practice of democratic centralism; and the 19th Party Congress, which set a new milestone in codifying the system as a disciplinary tool. I argue that while democratic centralism exemplifies the CCP's institutional plasticity and adaptive governance and is critical to understanding Party-driven constitutionalism in contemporary China, it also highlights an irresolvable paradox inherent in Party rule. Adaptability does not necessarily impart resilience. I conclude that the CCP's normatively unconstrained extra-constitutional leadership under Xi Jinping highlights the essentially and increasingly irrationalist aspects of its illiberal governance project.