What mechanism prevents one branch of the U.S. government from becoming too powerful?

The mechanism that prevents one branch of the U.S. government from becoming too powerful is checks and balances. This system is fundamental to the Constitution and ensures that each of the three branches of government—executive, legislative, and judicial—can monitor and limit the actions of the others.

For example, while the legislative branch makes laws, the executive branch has the power to veto them. Conversely, the judicial branch can review laws and executive actions to ensure they comply with the Constitution. This reciprocal oversight helps maintain a balance of power among the branches, preventing any single branch from overstepping its authority and becoming dominant.

The other options serve different purposes: separation of church and state addresses religious influence in government, direct democracy involves citizens making policy decisions directly rather than through elected representatives, and judicial review pertains specifically to the courts' ability to interpret the Constitution and invalidate laws that are contrary to it. While all of these concepts are crucial to the functioning of U.S. governance, it is the checks and balances that specifically focus on the interrelationships and limitations among the branches of government.