What is the principle behind the Constitution's division of power between federal and state governments?

The principle behind the Constitution's division of power between federal and state governments is called "federalism." Federalism is a system of government in which power is divided between a central authority (the federal or national government) and smaller political units (the states). The framers of the U.S. Constitution established this system to balance the power between different levels of government, aiming to prevent any single government or group from gaining too much control.

The Constitution outlines specific powers granted to the federal government, known as enumerated powers, which include the ability to regulate interstate and foreign commerce, coin money, provide for national defense, and conduct foreign relations. The Tenth Amendment further clarifies this division of power by stating that powers not delegated to the federal government by the Constitution, nor prohibited to the states, are reserved to the states or to the people.

This division of power allows for a system of checks and balances, in which both the federal and state governments can influence each other and thereby maintain a balance of authority. It also allows states to serve as "laboratories of democracy," where they can experiment with different policies and programs that may later be adopted at the national level if found successful.

Extra: Federalism, as a concept, offers several advantages. It allows the states to tailor policies to fit their populations' specific needs and preferences, which may vary widely across a large and diverse nation like the United States. Moreover, by having power spread out among different levels of government, federalism creates multiple access points for citizens' participation and representation, potentially increasing overall civic engagement.

One of the complexities of federalism is the ongoing negotiation regarding which level of government should take precedence in various areas of public policy. This discussion often revolves around the "supremacy clause" found in Article VI of the Constitution, which states that the federal law is the "supreme law of the land" and trumps conflicting state action.

The division also establishes a vertical separation of powers, complementing the horizontal separation of powers between the branches of the federal government: the executive, the legislative, and the judicial. This vertical structure helps protect individual liberties and prevents the concentration of too much power in any one part of the government.

The system can lead to disputes between state and federal governments, and the interpretation of federalism has evolved over time, often seen in landmark Supreme Court cases that have clarified the limits and extents of federal and state powers. Examples include cases on the commerce clause, the Affordable Care Act, and issues regarding civil rights, highlighting federalism's dynamic and adaptive nature in the American political system.