Ray v Blair 1952 seems to be the only time that SCOTUS ruled on a similar issue. This involved whether a political party could compel its electors to vote for the party's chosen candidate during a primary election, or whether they can vote as free agents. The decision allows parties to restrict how their electors vote.
The current laws that states are passing are quite different since these concern general elections and not party primaries. I suspect that Justice Jackson's dissent in Ray v Blair will carry more weight when these "end-around the Constitution" laws get challenged.
SCOTUS better rule on this quickly so that we don't have a debacle in 2020 when the Left tries to steal the election with this scam.
I just hope that President Trump is able to replace Ginsburg and/or Breyer (the two octogenarian far left liberals) before the issue reaches the Supreme Court.
I don’t think you can rule on it until it takes effect which would be after the 2020 election.