Thank you, sincerely. I should have paid more attention in Civics class eons ago but preferred World History.

I guess I'm just not grasping it completely as to why each state cannot enact a state-wide chosen method of in-person voting.

Would, by chance, the Elections Clause come into play? The Clause directs states to make regulations for the time, place, and manner of congressional elections, but it also states Congress has the right to supersede. There are some recent, interesting updates on this Clause. https://www.brennancenter.org/our-work/research-reports/independent-state-legislature-theory-explained

Thank you, sincerely. I should have paid more attention in Civics class eons ago but preferred World History.

Could each state enact a single in-person method for voting?

Would, by chance, the Elections Clause come into play? The Clause directs states to make regulations for the time, place, and manner of congressional elections, but it also states Congress has the right to supersede. There are some recent, interesting updates on this Clause. https://www.brennancenter.org/our-work/research-reports/independent-state-legislature-theory-explained