While ballot harvest rings are illegal and need to be busted up, I'm more interested to see if harvesters filled out those ballots themselves, or even went as far as swapping those ballots out with Rat voting ballots, or even simply inserted whole cloth fake printed ballots into the mix.
Ballot harvesting or not, a high chunk of mail-in ballots get voted anyway. I don't see where runners bringing the minority that are out are going to sway very many elections. Even in my former heavily Rat dominated county, mail-ins were generally about a third of the vote, the rest were election day, in-office, or satellite.
Usually around 90% of those were returned, the remainder were a mix of all parties, with Indies the ones most not returned. Not even in a large metro county would it be enough to influence an election over 1% difference.
That can't be their secret to winning. It's got to be fake or altered votes.