Article IV. Section 4 - Republican government
The United States shall guarantee to every State in this Union a Republican Form of Government, and shall protect each of them against Invasion; and on Application of the Legislature, or of the Executive (when the Legislature cannot be convened) against domestic Violence.
Yes, the Constitution requires every state to have a republican form of government. However, the is no Constitutional right to vote for President or Vice President of the United States.
I still don’t see a constitutional right to vote for president of the US.