caging
 A form of voter suppression. Employed by members of Republican Party, the term refers to the political tactic of using direct mail to target registered voters in order to invalidate registration and purge from voter rolls. With one type of caging, a political party sends registered mail to random addresses of registered voters of the opposing party. If the mail is returned as undeliverable - because, for example, either the voter refuses to sign for it, or the voter isn't present for delivery, or the voter is homeless - the party uses that fact to challenge the registration, arguing that because the voter could not be reached at the address, the registration is fraudulent. With the validity of the registration challenged, the voter's ballot cannot be counted until the voter proves that their registration is valid.
The voters targeted by caging are often the most vulnerable: soldiers deployed overseas, those who are unfamiliar with their rights under the law, and those who cannot spare the time, effort, and expense of proving that their registration is valid. On the day of the election, when the voter arrives at the poll to request a ballot, an operative of the party challenges the validity of their registration. Ultimately, caging works by dissuading a voter from casting a ballot, or by ensuring that they cast a provisional ballot, which is less likely to be counted. 

Monica Goodling cited her concern about "vote caging" in her written and oral testimony to the United States House Judiciary Committee on May 23, 2007, mentioning that Deputy Attorney General Paul McNulty "failed to disclose that he had some knowledge of allegations that Tim Griffin had been involved in vote-caging during his work on the president's 2004 campaign."