How do political parties remain vibrant organizations? This qualitative study of political parties in Chile, Costa Rica, and Uruguay explains how party vibrancy is maintained and reproduced over time. A vibrant party is an active organization that operates beyond electoral cycles, has clear symbols, and maintains a significant presence in the territory. The study identifies the complex interaction between four causal factors that account for the reproduction of party vibrancy: Purpose, Trauma, Channels of Ambition, and moderate Exit Barriers. Purpose activates retrospective loyalty among members. Trauma refers to a shared traumatic past that engenders retrospective loyalty. Channels of Ambition are routes by which individuals can pursue a political career. Moderate Exit Barriers are rules that set costs of defection at reasonable levels. The case studies suggest that, after a process of consolidation and stability, the presence of the four causal factors explains party vibrancy. The presence of the factors then sustains the reproduction of this vibrancy over time. The four causal factors are observed during a party’s “golden age.” Vibrant parties are resilient. Yet the study also shows that the ability of Trauma to forge loyalty decreases over time and that the long-term reproduction of Purpose can be elusive, as has been shown in Latin America. Older vibrant parties thus exhibit a combination of only Channels of Ambition and moderate Exit Barriers, and are less resilient than those that also have Purpose and/or Trauma.