In most states, voter registration information is a part of public records. For most places the information is available by written request. With the name, address and state of the person being searching most states have a limited search engine that will bring up some voter information. Voter Registration lookup by address for most statesa can be found here- Voter Registration Records/Poll Information.
Information available in voter records might include such things as unlisted phone numbers, birth dates or social security numbers, address, and party affiliation. Not every state has the same information available and for the most part these state sites are to check where the voting booths are located for a specific county. However, if you have a person's name, address and date of birth you can confirm that the information in hand is correct.
Voter registration can be a valuable tool in searching for people but also for use in genealogy. Older voter records in addition to the information listed above might also include length of residence in the state, county, ward or district, naturalization, race, telephone number, physical description, homeowner or renter, and possibly other bits of information. Finding out how long a person resided in one area is a good start to determining when they moved, thus a way to narrow the search and help to determine possible other leads in finding information on a person.
Voter information can be particularly helpful if census information is missing, or destroyed like the lost 1890 Census records, which were destroyed by fire. If a person is searching for older records then Ancestry.com, a subscription website has millions of voter registration records, and is working toward rebuilding the 1890 Census through the voter records.
These records can be a stepping-stone to other records, say if the person owned there home then there would be probate records, if a person owned property then there might be a will. The will might lead to other family members, or friends.
Being able to place a person geographically is another way to establish the neighborhood, and social standing of person. It is possible that other family members are near by and may still live in the neighborhood.
Voter registration records can be a crucial tool to advance a stalled search, find a long lost relative or for finding information when conducting a background check.