Bring the challenge to court. Say in court, under oath, the allegations that you claim in public. Accept the outcome of those cases. This has happened several times in recent presidential elections without triggering insurgency.

Trump's lawyers played a PR game. They made ostentatious allegations in public, but almost never presented the courts with a viable case -- and notably, didn't claim those allegations in court. The court is obliged to throw out cases without merit, and did so. And that makes it really easy to run out and claim that the court is tossing out your cases without them going to trial.