This article offers an interpretation of the crisis of the Bolivian Left in the mid-1980s, perhaps the most spectacular of all those suffered by the Latin American Left over the course of the decade. The author shows that the main distinguishing feature of the Bolivian case was the exceptional political power of the Central Obrera Boliviana (COB). It was this that enabled the union federation first to impose a highly expansive wage policy on the Unión Democrática y Popular (UDP) government, and then to veto its attempts to move towards a more realistic financial policy. The author goes on to argue that, in this second period, when the undesired consequences of the government's economic policy were sufficiently obvious to persuade the union to change its original strategies, the institutional structure that the COB had inherited from the past restricted and ultimately eliminated the union's strategic capacity. In this interpretation, the power of the union vis-à-vis a weak government, coupled with the union's own weakness as a corporate actor, gave rise to an accelerated process of institutional decline under the UDP government. This process was marked by the increasing prevalence of particularist and partial rationalities over the collective rationality, taking Bolivia to a Hobbesian situation, in which any actor capable of imposing a new order – however authoritarian or exclusive – would enjoy widespread support and legitimacy.