The moment the candidates clashed on NATO
Trump just shrugged when directly asked if he would stay in NATO. He did not even try to deny it later, or dodge the question like he often does. If Trump is openly taking an isolationist position, the risk is higher that he is going to act on it if re-elected. Even if the US does not officially withdraw, if the risk is more likely then both US allies and enemies are more likely to make decisions that assume the US will not be a reliable ally.
Democrats need to get their act together because this election is too important to lose.
Democratic elites will gladly allow the election to be thrown to Trump. It is clear neither Biden nor the establishment really care much about America or the World, as they are sleepwalking into a second Trump term.