Republicans and Democrats have already assured voters that the 2024 presidential election will indeed be considered illegitimate one way or the other, regardless of who wins.
If Republicans win, Democrats have promised that it is the result of Russian interference. If Democrats win, Republicans are certain to point to vague instances of voter fraud and follow through with meaningless lawsuits. In the event of a 269-269 tie, both are true.
Both political parties also said you should still be sure to vote in 2024 though, and end personal relationships with people who disagree with you politically.