They can’t go on indefinitely. It works because they attack each other in purity contests; the fight over speakers (twice) was one major front in this. Eventually, you run out of people to purify and need to invent a whole new issue. If you don’t, your support evaporates as people look for actual solutions to their problems.
There’s a strategy here that I don’t think has been fully utilized. If you can get the right to speedrun their purity contests against each other, you might be able to watch them eat each other quietly in a corner rather than dragging the whole country into fascism.