My dissertation examines why the common challenge of late development has generated starkly different responses in the Global South. I focus in particular on a cluster of cases that reacted to trade imbalances and political turmoil at the international stage with a combined agenda of economic nationalism, social progress and state-led industrialization, establishing what I term national developmentalist states. Why then, despite facing similar adaptive pressures, did these regimes markedly differ in terms of their durability and socio-economic policies? Through a careful study of such regimes in Turkey, Mexico, Argentina and Egypt during the middle third of the twentieth century, the dissertation specifies four variants of the national-developmentalist state and articulates how each type produced a distinct policy set with varying redistributive implications and political outcomes. I argue that where leaders invested heavily in building cohesive ruling-party and/or state organizations, regimes proved durable even with only moderate levels of economic redistribution. Where such institutions were weak, leaders could expand their popularity through excessive redistribution and risk elite polarization or establish a limited base but remain vulnerable to elite defections and popular opposition. These regime institutions were in turn conditioned by the intensity of intra-elite conflict and the differing ability of reformist elites to mobilize popular classes at the onset of their rule. I employ multiple strategies of inquiry, including paired comparisons and process tracing, to identify the causal mechanisms that link initial political conflict to institutions, and eventually to regime trajectories.