One of the crucial constitutional choices made in a democratizing or recently independent state is the structure of executive-legislative relations that forms into a parliamentary, presidential, or semi-presidential regime. Even so, only a few studies have sought the reasons for the establishment and least of all is known when it comes to the most recent of them: the semi-presidential one. The thesis aims to increase our knowledge on why and how semi-presidential regimes establish. This aim is approached through the use of three theoretical perspectives, including diffusion from abroad, the legacies incorporated in the domestic context, and the elites strategic bargaining expected by the perspective of transitional bargaining. Through its nested mixed methods approach, including two large-N and one single-case study, this thesis finds that semi-presidential establishment stem from all three perspectives: It is influenced by diffusion from international state networks, by legacies of post-communism and post-colonialism, as well as by the preferences of elite actors who attempt to act in a strategic manner. Semi-presidential establishment is thus a complex process and the application of the theoretical perspectives seem to depend on the level of uncertainty in the domestic context.
Through its findings, this thesis increases our knowledge on why and how semi-presidential regimes are established. In addition, they contribute to the field of diffusion, semi-presidentialism, but also to the larger field of institutional studies. Future studies should test the application of the conclusions on parliamentary and presidential regimes and on all semi-presidential regimes part of the post-colonial context.