Authoritarian survival is theorized and tested from an elite-centric standpoint, overlooking the role of ruling party organization structure. Focusing on one-party regimes, I expect party survival to be determined by its membership base stability. I exploit two variables available in OPAMED, party penetration in society and party membership stability, to test the hypothesis. Counterintuitively to previous research, I find that party breadth does not influence survival. However, I present strong evidence that membership stability over time significantly predicts ruling party survival. Ruling parties with decreasing membership within the last decade of government have higher chances of failure than those with stable membership. Among the reasons for ruling party demise there are citizens’ disenfranchisement, party organization jamming, and unrepairable external shocks. Further tests show that models predicting party failure without using membership stability hinder validity and increase model imprecision. The paper concludes that membership stability is key predictor for party survival.