This chapter focuses on the relationship between Machiavelli and Spinoza, using the concept of constituent power to analyze their contribution to the foundations of modern political thought. Both authors ground the stability of the State and its freedom on the popolo (Machiavelli) and the multitudo (Spinoza); this is not the generic people of modern constitutionalism, but rather the demos, the specific group inside the civitas whose power is exercised on, and sometimes against, other political subjects. Both authors aim at keeping alive the conflictual and constituent force that creates the juridical space of the State by recognizing the prominent role of social and political conflict. While Machiavelli explicitly argues for social conflict as the ground of political freedom, Spinoza develops his conflictualist approach through more implicit examples. Considering them together allows one to identify a radical democratic and revolutionary ground for the foundation of political modernity.