No "amendment" would do it, other than a constitutional amendment, which would be almost impossibly difficult. In fact, the push and momentum is exactly in the other direction now, with the left seeking to have states vote to enter a compact wherein they agree to case their electoral votes for the winner of the NATIONAL popular vote.

All states now require their electors to stay on board, either winner take all or proportionally based on the poplar vote of the state. Some states even have monetary fines. Fines of the sort in existence are pretty worthless, as they are ridiculously low. I don't know what the answer is, other than the USSC upholding the idea of bound electors with no discretion, combined with some state law changes that call for removal of a faithless elector, the nullification of the vote, and a revote by an alternate elector. A fine is meaningless if the faithless vote is allowed to stand.

All of this, of course, would not be an issue without the relentless cheating and evasion of rules and norms by the left.