This article analyses how institutional and contextual factors explain the approval of presidential initiatives – presidential legislative success – in highly disciplined and cartelized assemblies. Of particular importance is to test whether public opinion, the electoral cycle and the use of different institutional rules affect the approval of presidential initiatives in Congress. Using a multilevel Bayesian model of legislative success, I model bill approval rates at individual and aggregate levels. This strategy is extremely flexible, allowing us to disentangle the different institutional and contextual factors that determine the approval of presidential initiatives in the Argentine Congress.