The contribution will attempt to reflect on the interplay in recent theories of populism and crowd psychology between the ideas of mob and crowd on the one hand, and those of mass and people on the other. Using an approach deriving from the history of ideas, it will outline two fundamental aspects of the complex and ambivalent interaction between the concepts of people, crowds, masses and mob: first, the transformation of the protesting crowd or mob into "the people," the legitimate source of sovereignty; second, the distinction between regressive crowds and mobs and progressive masses and peoples, stated both explicitly and implicitly in crowd psychology and populist theory. This article will also aim to highlight an idea that has come to the fore in much of the recent literature on populism. It has long been observed that populism opposes "corrupted" elites and the "honest" people. But it has recently been observed that a major source of populist mobilization is a distinction, within "the people," between a "positive" people and the "others," the plebs who are left outside the dynamics of any kind of political representation. The article will show that this distinction is fundamental in order to understand not only the construction of populist political identity, but also the dynamics of the mobilization of new movements, which claim to take charge of the political processes and change the rules of the game.