That raises an interesting possibility. Suppose Biden wins and rigs things so the Democrats win all elections and the Republican party collapses. What would then happen is that you'd have factions inside the Democrats. One of those will be the AOC branch, one the Clinton/Biden branch and one would be Blue Dog crypto Republicans.
And of those, the AOC branch looks like the one which would fail.
So you'd still have Democrats and Republicans just under different names. You can see that in the way the names of the parties have changed. Actually, come to think of it the ideologies have changed in a pretty radical way too, it's just that takes longer. A lot of people in this thread have said 'If the Republicans screw this up, they're finished'. Well, maybe they will screw it up and they will be finished. However, the millions of people who voted for Trump won't just go away. And the Democratic Party is not democratic centralist - it's like a sack full of cats. Same with the Republican party to be honest. US parties have very lax internal discipline. It's one of the upsides of the way politicians have a very strong incumbent advantage, which is otherwise bad.
So even if hypothetically speaking, this election produces a Democrat one-party state and that is very much the worst of all the possible outcomes, I predict that will not last.