This applied to the UK in recent elections. Conservative voters would seldom if ever go over to Labour, regarding them as a collection of squabbling brats who obsess with PC and have a tendency to pander to the far left. Corbyn managed to snatch defeat from the jaws of victory, against both a highly unpopular candidate and party, by insisting on his ideological point of view. Biden is nothing like any British politician in a similar position, but he too has the “we don’t like our man, but we won’t vote for you” factor. Or they don’t vote at all.
Given the vagaries of the electoral college, I wonder if Trump might just pull off a narrow victory, despite having fewer actual votes.The Brexit referendum looked like a narrow win for remain, until the votes came in. Could it happen with Trump? Needless to add, I hope not, but in four years I have seen three examples of the worst possible scenario happening.