I might be wrong, but I do not think this has ever happened before. If both Biden and trump want their parties nominations, they can have them. Especially trump might not run, but if he does, he will be the Republican nominee. Other candidates have two years to think about it, before they really have to decide... But they should be making plans right now. Given the locks on the nominations, many will decide not to run.

In the past, the sitting President has a lock on the nomination. That is not unusual, but then the other parties nomination is up for grabs. Presidents who lose reelection are almost never allowed to get the nomination again, much less have a lock on it like trump does. Can you imagine Bush Senior running again in 1996, or Carter running again in 1984?

We all know the reason for this, Republicans have not admitted they lost. They do not feel a need to change their strategy, because they believe it is a winning strategy.

Democrats also believe they won, which is more reasonable, because Biden is sitting in the White House.