Focusing on the relatively longstanding experience of neighborhood councils in the Uruguayan capital of Montevideo (1993–), this research note seeks to analyze how sustainable democratic innovation is and to explain subsequent results. Sustainability is assessed through the evolution of citizens’ participation in elections and through the number of candidates who apply to become neighborhood councilors. For both indicators, a consistent decline in the levels of participation over time is found. This is deemed to be a consequence of an institutional design that seriously limits the performance of neighborhood councils in terms of their influence in the decision-making process and their acquisition of legitimacy and political capital.