Despite the fact that semi-presidentialism has proliferated as a regime type its nature remains relatively contested. Maurice Duverger was the first to define the concept. According to him, a political regime is considered semi-presidential if the constitution which establishes it combines three elements: 1) the president is elected by universal suffrage; 2) he possesses quite considerable powers; 3) he has opposite him, a prime minister and ministers who possess executive and governmental power and can stay in office only if the parliament does not show its opposition to them (Duverger, 1980, p.165). Following these constitutional norms, Duverger identified seven semi-presidential regimes in 1980, namely Austria, Iceland, Ireland, Finland, France, Portugal and Weimar Germany. <p>This definition of semi-presidentialism has been criticized in subsequent studies for two major reasons, namely for using only constitutional rules, and for not stating clearly what &quot;considerable Presidential powers&quot; mean.&nbsp; Other attempts at clarifying the concept of semi-presidentialism have sided with Duverger's reliance on constitutional norms (Shugart and Carey, 1992, 2005; Elgie, 1999). However, Duverger's definition remains problematic due to the fact that it is unclear what &quot;considerable presidential power&quot; means. </p>Elgie reformulated Duverger's criteria by eliminating the phrase on considerable powers. According to him, a regime is semi-presidential whenever the President is popularly elected on a fixed mandate and co-exists with a prime-minister and a government which are responsible to Parliament. Although it is true that Elgie's definition is sufficient in order to categorise a regime as semi-presidential, it is insufficient to distinguish between semi-presidential regimes. In order to do that, Shugart and Carey (1992), and Shugart (2005) have opted for effectively defining Duverger's notion of &quot;considerable&quot; powers. According to these authors, within the range of powers that a President may have, one is most crucial to define his position within the regime, namely his ability to dismiss the government. Regimes are labeled premier-presidential, if the prime minister and the government are exclusively accountable to the Assembly. In these regimes, although the President nominates the Prime Minister and the government, its subsequent survival depends on the Assembly, thus conditioning Presidential choice and limiting his hold over the government. This literature review makes clear that constitutional norms are the necessary starting point for the analysis of Portuguese semi-presidentialism, and also show that the dispositional features are essential to characterize the sub-type of semi-presidentialism to which Portugal belongs too. Of course, other features of the political regime, namely its genesis, the evolution of the party system and successive Presidents' relationship with that majority should be used to complete our understanding of the functioning of the political system. Shugart and Carey's work thus seems especially relevant to trace possible changes which have occurred in Portugal since adoption of a semi-presidential constitution in 1976. Before we proceed to present the institutional framework of the Portuguese political regime, we provide a brief overview of the way in which Portugal has been characterized in the literature on semi-presidentialism.