> there's a lot of people who seem to operate on the presumption that in the long term, their side is going to have complete control of the government indefinitely

I think you are confusing outcome for mechanism. The idea is that once their side wins, they'll clamp down so hard on wrong-think that the other side effective ceases to exist. It will be like elections under a dictator: sure there's another party, but if you vote for them you get a free trip to the re-education camp and get erased from all databases.