I guess the correct term is 'ballot harvesting'.
How Ballot Harvesting Works
Ballot harvesting begins when a voter is given or requests to receive his or her ballot by mail. Once the voter’s ballot arrives, he or she has the opportunity to complete and return the ballot before the ballot return deadline.
While the voter still has possession of his or her ballot, a ballot harvester will approach the individual (often with the aid of a voter list to know which voters received their ballots by mail) to offer the voter assistance in completing and/or returning the ballot. If the voter consents, the ballot harvester will collect the completed ballot and return it for the voter. Ballot harvesters will repeat this process to deliver as many ballots as possible before the deadline, which is usually Election Day.
When electors vote by mail, they typically have a few options for returning their completed ballots: by mail, by dropping them off at a polling location, or by delivering them to a designated drop box. Ballot harvesting, also known as ballot trafficking or third-party ballot collection, occurs...
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