Hat is popular sovereignty? why was this an important new idea at the time of the constitution was written?

Popular Sovereignty is the idea that power comes from the People. Prior to the Constitution, Power came from a King, Queen, or special class (nobility or priests). Power was concentrated within one person. The idea that a common person had the same rights as one from a noble class was revolutionary and went against all the teachings of the day. The idea that common people had the power to overthrow a ruler for being corrupt was even more revolutionary. The Constitution was often referred to as the "Grand Experiment" because none of the Founding Fathers were sure if it would actually work.

Who it was like back then