well, if everything is done according to each State's election laws, then everyone should be fine with the results.
But when you board up windows and purposely block poll watchers from the supervising and get caught stuffing ballot boxes and shred mail-in ballots, allow late mail-in ballots, double counting the same ballot and disregard poll workers reports of violation of chain of custody of ballot boxes, fake ballots, etc. Then that's election fraud.