each state must have a republican form of government
This clause, sometimes referred to as the Guarantee Clause, has long been at the forefront of the debate about the rights of citizens vis-à-vis the government. The Guarantee Clause mandates that all U.S. states must be grounded in republican principles such as the consent of the governed. By ensuring that all states must have the same basic republican philosophy, the Guarantee Clause is one of several portions of the Constitution which mandates symmetric federalism between the states.
Article Four of the United States Constitution