From your source I keep seeing this world voter caging so I googled it.
Voter caging is a method of challenging the registration status of voters to potentially prevent them from voting in an election.
It refers to the practice of sending direct mail to addressees on the voter rolls, compiling a list of addressees from which the mail is returned undelivered, and using that list to purge or challenge voters’ registrations on the grounds that the voters do not legally reside at registered addresses. This typically results in the voters' having their votes discarded or submitted through the use of provisional ballots requiring further registration confirmation
http://en.wikipedia.org/wiki/Caging_(voter_suppression)
Here's the source you just posted
DNC v. RNC Consent Decree
In 1982, after caging in predominantly African-American and Latino neighborhoods, the Republican National Committee and New Jersey Republican State Committee entered into a consent decree with their Democratic party counterparts. Under that decree and its 1987 successor, the Republican party organizations agreed to allow a federal court to review proposed “ballot security” programs, including any proposed
voter caging.
DNC v. RNC Consent Decree | Brennan Center for Justice
Now my question is this what does asking for an ID when yu go to vote have to do with voter caging?