“But each party has its slate of electors who commit to voting for a specific candidate. In effect the State is changing the commitment of individual electors. It is important to read the decision to sort that out. Have you read it?”
In the case of the national popular vote, the state legislator would be forcing electors to vote against the will of the people, effectively disconnecting the voters from their electors. That could easily be viewed by SCOTUS as conflicting with section 2 of the 14th amendment. Completely different issue. When states force electors to vote with the will of the people, there’s no conflict with the 14th amendment.
Will of which people? The state or nationally? See my post #55. NPV seems to believe they are unaffected by the ruling.