Many vivid anecdotes of purported voter fraud have been proven false or do not demonstrate fraud.
Although there are a few scattered instances of real voter fraud, many of the vivid anecdotes cited in accounts of voter fraud have been proven false or vastly overstated.
In Missouri in 2000, for example, the Secretary of State claimed that 79 voters were registered with addresses at vacant lots, but subsequent investigation revealed that the lots in question actually housed valid and legitimate residences.
Similarly, a 1995 investigation into votes allegedly cast in Baltimore by deceased voters and those with disenfranchising felony convictions revealed that the voters in question were both alive and felony-free.
Many of the inaccurate claims result from lists of voters compared to other lists - of deceased individuals, persons with felony convictions, voters in other states, etc.
These attempts to match information often yield predictable errors.
In Florida in 2000, a list of purged voters later became notorious when it was discovered that the “matching” process captured eligible voters with names similar to - but decidedly different from - the names of persons with felony convictions, sometimes in other states entirely.
A 2005 attempt to identify supposed double voters in New Jersey mistakenly accused people with similar names but whose middle names or suffixes were clearly different, such as “J.T. Kearns, Jr.” and “J.T. Kearns, Sr.,” of being the same person.
http://www.brennancenter.org/content/resource/policy_brief_on_the_truth_about_voter_fraud/