Historically, that’s exactly what you have to do to topple an autocrat. Around the world, autocrats come to power when both major parties are seen as completely corrupt and ineffectual. Usually the only way to defeat them is to completely abandon both parties. Look at Orban’s recent defeat in Hungary. He wasn’t defeated by the captured opposition, the analog of the US Democratic party. He was defeated by a united front of anti-authoritarian voters that spanned across the political spectrum.

The idea that you can just keep voting for the captured opposition has no basis in historical fact. You can’t defeat a dictator by campaigning for a potemkin opposition also run by that dictator.