How do new social policies emerge? The literature on developed countries has put forth important assumptions about changes in welfare policies, particularly building on the work of Esping-Andersen. However, discussion of social protection policies in middle-income countries underscores that rising policy innovations derive mostly from exogenous dimensions (external ideas and factors). In examining Mexico's Oportunidades and Brazil's Bolsa Famıĺia, one main question is addressed: What causal mechanisms underlie the rise of policy innovations that are not derived from exogenous dimensions? This article proposes moving beyond the argument in which international influence versus domestic politics are in opposition, and it suggests instead to compare empirical cases in different contexts, specifically by exploring the process of endogenous institutional changes using the example of conditional cash transfer (CCT) programs. By exploring recent theoretical contributions to institutional changes, the article identifies two critical aspects: (1) the rise of a dominant advocacy coalition favoring an ideology that promotes human capital as a key factor in the formation of national CCT programs in Brazil and Mexico; and (2) advocacy coalitions achieve similar results in terms of institutional changes in Brazil and Mexico, despite having different strategies and patterns of change. How do new social policies emerge? How can we explain the rise of policy models? The literature on developed countries has put forth important assumptions about changes in welfare policies by grouping social policies into distinct regimes or spheres of the welfare state (Esping-Andersen 1990; Huber and Stephens 2001). However, changes to social protection policies in middleincome countries-particularly in Latin America over the last few decades-present a major challenge for welfare state researchers (Carnes et al. 2007). By making use of the Advocacy Coalition Framework (ACF) (Sabatier and Jenkins-Smith 1993; Sabatier 1999) and recent theoretical contributions to institutional changes, this article allows for deeper understanding of