The phrase "do ordain and establish this Constitution" in the preamble to the United States Constitution is an expression of popular sovereignty. Political authority in the United States is derived from the people rather than from God or any other source. The government can only govern so long as it reflects the will of the people and has their consent to do so.
Popular sovereignty is first expressed in the Declaration of Independence as the principle that governments derive "their just powers from the consent of the governed." A government that does not respect the will of the people it governs loses its legitimacy and may be justifiably replaced. In the Declaration, the colonists expressed their belief that the British had violated their rights and ignored their wishes.
The Constitution codifies this principle into law. The authority of the federal government is explicitly derived from the consent of the people themselves as expressed through their participation in the political process. Popular sovereignty does not have to involve direct democracy, but the people must have the opportunity to elect their representatives. When the Constitution was ratified as the supreme law of the land, this was the first and most important instance of popular sovereignty in the United States.