Usually, caging occurs when an official-looking, non-forwardable piece of mail is sent to a group of registered voters, often to minorities and students. The parties involved in caging then compile a list of voters whose mail was returned as undeliverable. On Election Day, these organizations will use the undeliverable mail to challenge voters at the polls, utilizing law enforcement and attorneys to support their challenges.
The goal of caging is two-fold. First, is to force as many voters as possible to cast provisional ballots, which require voters to follow-up the day after an election for the ballot to be counted. Historically, about 35% of all provisional ballots are never counted. Additionally, voters whose registration is challenged at the polling place are unlikely to have the required material to complete an Election Day registration, meaning the voter will be turned away at the polls.
The second goal is to create long lines at the polling place as the caging operation challenges voter after voter. Many people cannot afford to sit in line to vote for hours on end. Long lines discourage voters and many simply leave without casting a ballot.
Voter caging is a violation of the Help America Vote Act and is illegal.
"A little fill here and there may seem to be nothing to become excited about. But one fill, though comparatively inconsequential, may lead to another, and another, and before long a great body may be eaten away until it may no longer exist. Our navigable waters are a precious natural heritage, once gone, they disappear forever," wrote the Wisconsin Supreme Court in its 1960 opinion resolving Hixon v. PSC and buttressing The Public Trust Doctrine, Article IX of the Wisconsin State Constitution.