Really?
Really. The Constitution does not require a state to divide its electors among multiple candidates based on the popular vote within the state.
Constitutional?
Probably so. In the current system the voter selects a slate of electors who are pledged to vote for a particular parties candidates. Some states are winner takes all and a few states apportion the electors according to the popular votes, their choice.
This system will instruct the electors to vote for the winner of the popular vote, either by empaneling the slate that is committed to the popular vote winner or by extracting a pledge from all electoral candidates to cast their vote as the states voters direct. Probably Constitutional, but we won’t know for sure until its tested.
The real problem comes with the behavior of the electors. In the past, a few electors have broken their pledge. Never in a way to sway an election, but as their own private protest. This system will make it tempting for electors to change their votes if it didn’t come out the way they wanted. What will happen then? Not clear, but I think that the Constitution envisioned that the states would select wise and learned men as electors and they in turn would elect the man best suited to be President (women not in the mix in those halcyon days)