You are correct. The selection process is constitutional. Article 2 Section 1 reads “Each State shall appoint, in such Manner as the Legislature thereof may direct, a Number of Electors”. If the states want to throw away their power and give the electors to the majority vote (fraud) winner, then they can.
However, I believe forcing the electors to vote for a certain candidate is unconstitutional.
Rightly or wrongly, the Supreme Court has another view.
Ray v. Blair, 343 U.S. 214 (1952)
In any case, I don't see the proposed law as imposing any more force than the old law. Did I miss something?