Many countries have ran national campaigns to boycott a vote if they consider it illegitimate. Although it would almost certainly lead to a Dem landslide, it would delegitimize their win for that cycle, but also serve to highlight how much of their normal base is the result of fraud. It's not enough simply to say you won't vote because there's no point, you have to organize a well-funded campaign to ensure the vast majority don't and make damn well sure everyone knows the reason. Could such a thing even be pulled off in the US though?