The spread of fake news on the Internet, the educational divide, the adverse effects of the economic crisis and the emergence of international terrorism are often ranked among the factors that led to the rise of populism. However, quite rarely it is called into question whether (and how) the distrust of mainstream political parties had an impact on the rise of populism across the Western democracies. Adopting a constitutional law perspective requires looking at the rise of populism through the lenses of the crisis of democratic representation. The paper aims at exploring the Italian scenario, where the anti-establishment Five Star Movement has grown up as leading populist force fostering a direct political participation of voters through the use of the Internet that is supposed to bring, in the long run, to political disintermediation. In this respect, the goal of the paper is to explore from a constitutional law perspective the grounds on which the rise of this anti-establishment movement has relied and the constraints that the Constitution may place on the populist surge.