This paper questions the orthodox institutionalist perspective and its reliance on rational choice theory in the literature on Latin American populism. Examining two articles on populism by Kurt Weyland and Kenneth M. Roberts, it argues that this dependence on rational choice theory promotes an overemphasis on elite leadership to the detriment of ideology and popular agency. Using a Marxist perspective, based on Laclau (2005) and using two case studies, President Fujimori of Peru (1990-2001) and President Chávez of Venezuela (1999-present), this paper argues that movements articulated with neoliberalism have much lower levels of popular involvement, while those influenced by socialism have a greater balance between populist leadership and bases, hence proving that ideology does have a determining impact on populist formations.