Is the worst case scenario in the presidential election that the winner of the popular vote loses the election? If I had to predict the most dangerous scenario that might be it.
But worst case? Remember, as the late Mayor Daley once remarked, somebody will be elected.
You are not nearly imaginative enough for dangerous or worst case scenarios.
I would say that a 269-269 Electoral College tie would be worse than something that has happened several times in American history, most recently in 2000.
Worst case? VP Biden is re-elected in the Senate on a 51-50 vote as the House deadlocks on a 269-269 vote tie. President Biden takes the oath.