The Constitution gives the states total control over how electors are appointed. They could have lotteries should they wish.
But that doesn’t answer the question I have: how can an “elector” in Pennsylvania say to Pennsylvanians that “..it doesn’t matter if more of you voted to elect a Republican; the Democrat got higher votes in other states (of course, I as a Pennsylvania elector have no idea if the “popular vote count” is accurate from other states), and I also have no idea how I can verify that vote count from other states - but I need to adhere to that because all of your votes are now just my vote. Your voting really doesn’t matter. Only the people in really populous states matter, so I’m going with them”.
How is that not a nullification of every voter in the state??