<p>Since the Cold War, many developing countries have experienced a new wave of democratization, with latecomer states adopting liberal reforms to establish or enhance democratic systems centered on competitive elections. After the establishment of democratic systems, some developing countries have achieved political stability, economic development, and social progress; however, other latecomer democratic countries have fallen into governance dilemmas such as social cleavage, economic stagnation, and state corruption. To address what drives differences in democratic governance among developing countries, this paper employs new institutionalism as its main theoretical foundation, exploring how institutional co-optation of power elites affects democratic governance through the interactive dynamics between actors and institutions. By comparing Chile and Argentina, the author argues that when a democratic system achieves institutional co-optation of power elites, these elites tend to favor institutional alliances and formal cooperation. This behavior helps enhance state capacity and promotes the orderly development of democratic governance. Through this comparative study, the author proposes a type of democracy in which “institutional co-optation of power elites” serves as the main variable. This serves to integrate and summarize the institutional constraints of co-optation while exploring the potential impact of interactions between power elites and democratic institutions in developing countries on democratic governance.</p>