@Griffith
Depends on the mechanism they're using and how much control they have over the whole process. Ballots that are too obviously fishy can get thrown out if they run into a judge who isn't a complete partisan shill. There's only so many names on the voter rolls, so many absentee ballots. A lot of what they do with ballot harvesting is technically legal, where they fill out ballots on behalf of real people who for whatever reason aren't capable of voting on their own, whether it's the elderly, druggies, etc.