Which concept ensures that no branch of government becomes too powerful?

The concept that ensures no branch of government becomes too powerful is checks and balances. This principle, embedded in the U.S. Constitution, establishes a system where the powers of each branch—executive, legislative, and judicial—are not only distinct but also provide mechanisms for limiting each other's authority. For instance, the legislative branch can create laws, but the executive has the power to veto those laws. Furthermore, the judicial branch can review laws and executive actions to ensure they comply with the Constitution. This continual oversight and interaction among the branches prevent any single branch from accumulating excessive power, promoting a balanced and accountable government.

While separation of powers is related and important for designating distinct responsibilities to each branch, it is the system of checks and balances that actively prevents the overreach of power through inter-branch competition and collaboration. Federalism refers to the division of power between national and state governments, while direct democracy involves citizens exercising power directly rather than through elected representatives; neither of these concepts specifically addresses the balance of power among the branches of national government.