I think if Trump is forced off the ballot by Democrat finagling through the courts, or whatever, and that's obvious--which it is right now--that as much as 50% of the usual 55 to 60% of people that vote in a presidential election won't or will fill in something like "None of the above" for President.
That means if Biden wins such an election it's on something like 30% or less of the total possible electorate. That will be a national disaster.
Less of one than if Trump were to win or take over after a loss.