Why are participatory institutions implemented nationwide in some countries but only adopted on paper in others? I argue that the national-scale implementation of a critical subtype of participatory institutions, Binding Participatory Institutions (BPIs) --is dependent upon the backing of a strong institutional supporter, normally a political party. In turn, I argue political parties will only implement BPIs nationwide when they perceive an electoral benefit from doing so. This occurs when 1) significant societal demand exists for BPIs, and 2), the party’s political opponents are not capable of taking advantage of BPIs for their own electoral gain. Under these conditions, parties will place a lower value on the political costs than on the potential benefits of BPI implementation. I test this theory through two detailed case studies of Venezuela and Ecuador, drawing upon a wide range of qualitative and quantitative data, including 159 interviews with key national-level actors and grassroots activists involved in the adoption and implementation of BPIs in these countries.