It’s never happened and we think it would be illegal.
Well before an election begins, a legislature could decide to remove the people from the process that selects electors. The last state to flip flop like this was Florida in the 19th Century. In 1860, it held a popular vote for President. But after Florida seceded during the Civil War it didn’t participate in the presidential election of 1864. After Florida rejoined, it passed a law well before the 1868 election allowing its legislature to directly appoint electors. Florida then reversed course again before the 1872 election and held a popular vote for President. It has held a popular vote for President ever since. But, in theory, Florida could pass a law before the 2024 election and decide its legislature should appoint electors directly.
But after an election has begun or after it’s been held, however, it’s less clear that the state may retroactively change the method of appointing electors. The best authority suggests it could not.
First, such a procedure would seem to violate 3 U.S.C. § 1, which requires that states that hold elections select their electors on election day. If a legislature attempted to change the slate of electors after Election Day, it would miss this deadline and violate federal law.
Second, there’s a strong argument a state legislature’s substitution of its own slate of electors after Election Day would violate the Due Process Clause of the Constitution. The Due Process Clause protects citizens’ expectations under state law that they will be able to exercise their right to vote and have that vote counted. If the legislature elevates its own preferences over those of the voters by retroactively changing state law, this right would be violated.
Both limitations would depend, however, upon the courts intervening. It is possible the Courts would view the legislature’s actions as a “political question,” not subject to judicial review.
However, a state could claim that the election has “failed” under the “Failed Election” provision of Title 3. As discussed, below, states could cite this provision as an authorization for sending their own slates of electors to Congress.