The judicial power shall extend to all cases, in law and equity, arising under this Constitution, the laws of the United States, and treaties made, or which shall be made, under their authority;--to all cases affecting ambassadors, other public ministers and consuls;--to all cases of admiralty and maritime jurisdiction;--to controversies to which the United States shall be a party;--to controversies between two or more states;--between a state and citizens of another state;--between citizens of different states;--between citizens of the same state claiming lands under grants of different states, and between a state, or the citizens thereof, and foreign states, citizens or subjects.
Elsewhere, it provides that the Supreme Court has original jurisdiction of certain types of cases, including cases in which a state is a party. That original jurisdiction is not exclusive, though. It can be delegated to a lower court. The paragraph after the one you quoted spells out what is original for the Supreme Court and what is appellate. Cases involving states have original jurisdiction. For that reason, it is a very smart move to have Texas and other states sue the states trying to steal the election.