The framers had lived under a king who claimed too much power and then under the Articles of Confederation, which gave the national government too little. Their solution was to divide federal power among three branches, each with its own source of authority and its own means of resisting encroachment by the others. James Madison put it plainly in Federalist No. 51: ambition must be made to counteract ambition.
This guide walks through each branch, the checks that bind them together, and the places where the lines between them are being contested today. Every institution and idea links to a full entry.
Congress makes the laws, raises and spends money, declares war, and oversees the rest of the government. It has two chambers by design: the House, apportioned by population with two-year terms, and the Senate, with two members per state and six-year terms. Congress also has its own support agencies, such as the Congressional Budget Office and the Government Accountability Office, which give it independent sources of information about the executive branch.
The President is head of state, head of government, and commander in chief, charged with taking care that the laws be faithfully executed. The Vice President stands first in line of succession. The President leads an executive branch of fifteen Cabinet departments, dozens of agencies, and the Executive Office of the President, together employing more than two million civilians. How much control the President should have over that sprawling administrative state is among the most debated questions in government today.
Article III creates one Supreme Court and lets Congress establish lower courts, which today include 13 courts of appeals and 94 district courts. Federal judges serve during good behavior, effectively for life, to insulate them from political pressure. Since Marbury v. Madison in 1803, the courts have claimed the power of judicial review, the authority to strike down laws and executive actions that violate the Constitution.
The Constitution opens with the branches in order of the framers' priorities: Congress first, then the President, then the courts. Its design rests on a few principles that run through everything that follows: power divided among branches, each able to check the others, a national government limited to the powers it is granted, and authority that flows from the people. The Federalist Papers remain the classic explanation of why the pieces fit together as they do.
The separation is not absolute. The President can veto bills, and Congress can override vetoes. The Senate confirms judges and senior officials and approves treaties. Congress can investigate the executive, control its funding, and impeach and remove officials, including judges. The courts can invalidate laws and actions, and the President and Congress can respond by changing laws, proposing amendments, or reshaping the courts through appointments. Landmark cases have drawn many of these lines.
Many current controversies are boundary disputes. Should independent agencies be insulated from presidential control, or does the Constitution give the President authority over all executive officers? How far does presidential immunity extend? Should courts defer to agencies on the meaning of statutes? When Congress is gridlocked, how much may Presidents do on their own? Supporters of a strong presidency and defenders of congressional and judicial checks give very different answers, and the entries below lay out both sides.
Each branch has its own guide coming. Follow lawmaking step by step in how a bill becomes law, meet the executive departments in the fifteen Cabinet departments, and see the courts at work in how a Supreme Court case works.