In this paper I claim that “authoritarian constitutionalism” is not an oxymoron as it may seem. A series of authoritarian practices have always characterized constitutionalism. Among them, I examine the case of calls for executive dominance in the context of a limited, although not fully erased, separation of powers. After briefly showing that these calls are well alive today, I consider the ideas of the Italian constitutional lawyer Costantino Mortati (1891-1985). A leading scholar in his country, who contributed to drafting of the current Constitution, in his early writings in the Thirties he tried to conceptualize Italy’s transition from a liberal State to the Fascist regime and to reconcile some degree of separation of powers with a strong executive governing in an effective manner, instead of merely executing the will of the Parliament. This, I argue, exemplifies how calls for executive dominance are not new in modern constitutionalism, but part of its “dark” legacy.