The United States is the world's oldest surviving federation. It is a constitutional republic and representative democracy, "in which majority rule is tempered by minority rights protected by law." The government is controlled by a system of checks and balances from the United States Constitution. The constitution is the country's main legal document. There are three branches. They are the "executive branch", the "legislative branch", and the "judicial branch". State governments and the federal government work in very similar ways. Each state has its own executive, legislative, and judicial branches. The executive branch of a state government is led by a governor, instead of a president.