The Constitution. The Preamble also answers the

The Preamble to the Constitution contains powerful language that is the bedrock of American political tradition. The opening line: "We the People of the United States" proclaims that the states remain in a unity and that they are not independent of one another. With these words the loose confederation of independent states ceased to exist after ratification of the Constitution. The Preamble also answers the question of the source of power of the government: the power comes from the people, not from the states. The phrase "[I]n Order to form a more perfect Union" implies that at the time of forming the country, the Articles of Confederation were weak in governing a growing nation. Next come the general goals for the American nation (originally set up by the Framers): "establish Justice, insure domestic Tranquility, provide for the common defense, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity". The following words: "do ordain and establish this Constitution for the United States of America" pose the formal creation of the new government after the ratification.
Article I vests all legislative powers in the Congress and establishes a bicameral legislature, consisting of the Senate and the House of Representatives. It also sets out the qualifications for holding office in each house, the terms of office, methods of selection of representatives and senators, and the system of apportionment among the states to determine membership in the House of Representatives. The Article I, section 8 contains enumerated powers and elastic clause.
Article II vests the executive power- the authority to execute the laws of the nation in a president of the United States. Section 1 sets the president's term of office at four years, explains the electoral college, states qualifications for office and describes a mechanism to replace the president in case of death