Here's a passage from 2000 that clearly shows that state legislatures have the power to send whatever slate of electors that they choose to at any time ---------The unanimous order issued by the US high court on Monday, which vacated the Florida Supreme Court's first ruling on hand recounts and sent the issue back to the Florida court for re-evaluation, contains an important passage which presents the state legislature as the ultimate arbiter of the presidential contest in Florida.------
State legislatures just need to decertify the electors that the governors sent and they've every right to do so.----In fact, it's incumbent upon them to do so.
State legislatures cant do that after the election has taken place.Any changes they want to make has to be before the election.
From Bush v Gore--- The State, of course, after granting the franchise in the special context of Article II, can take back the power to appoint electors. See id., at 35 (“[T]here is no doubt of the right of the legislature to resume the power at any time, for it can neither be taken away nor abdicated”)