I argue that the core difference between popular constitutionalism and populist constitutionalism lies on the degree of anti-elitism supporting constitutional changes. Popular constitutionalism can be defined as comprising those constitutional theories, mostly carried out by US constitutional scholars starting from the late 1980s, who support an anti-elitist reading of the constitution and acknowledge the role of ordinary people in the system of checks and balances. All authors espouse the idea that ordinary constitutional devices, such as checks and balances, are not sufficient per se to avoid exploitation by elites. Populist constitutionalism radicalizes the ambitions of popular constitutionalists and propose to use constitutional change mainly to radically neutralize elite power and sometimes to entrench the new populist elite. Unlike popular constitutionalism, populist constitutionalism is infused of rigidity and legalism and poses a threat to liberal values.