The National Popular Vote Interstate Compact is an agreement between several US states to award their electoral college votes to the winner of the national vote. This agreement is designed to only take effect once enough states have ratified it that they have over 50% of the total electoral college electors.
Before the NPVIC comes into effect, electors are pledged to vote for the winner of their state's presidential election. If the NPVIC was ratified after election day and before the day the electoral college votes, what would happen (assuming that the Supreme Court did not judge it an illegal pact)? Would the participating state's electors now vote for the winner of the popular vote, or would they still vote for the candidate they pledged to vote for on election day, so that the NPVIC would functionally only change things for the next presidential election?