"That's tens of thousands of people in a state that decided a presidential contest by a few hundred votes (in 2000)," says Slater, whose group was one of the parties that sued Florida.
Florida's voter-registration list isn't new to controversy, of course. In 2000 a contractor hired to weed out convicted felons used broad criteria to match voter names against correctional records and swept up thousands of the wrong people. The same problem occurred in 2004.
Slater cites another troubling trend emerging with the implementation of statewide databases.
Several states have begun comparing databases for duplicate records of existing voters, then purging voters they believe have moved and registered in another state. The problem, Slater says, is the methods used can yield false positives, and officials are deleting voters without contacting them to verify that they've moved, or waiting for two federal election cycles to pass, which are requirements under the National Voter Rights Acts of 1993.
In 2006, Kentucky's attorney general successfully sued his state's board of elections after officials compared their list to ones from South Carolina and Tennessee and purged about 8,000 voters who appeared to have registered in those states at a later date than their registration in Kentucky and were presumed to have moved.
Project Vote is investigating Kansas, Louisiana and South Dakota for similar activity. Minnesota, Iowa, Missouri and Nebraska have also been comparing lists.
"That is a trend that will accelerate, but there are inadequate safeguards, and I think it's very, very dangerous," Slater says.
To address some of the issues that may arise at polls in November, voting groups are advising voters to double-check their registration status before their state's registration deadline (.pdf), to bring ID to the polls in case questions arise about their eligibility, and call 866.MYVOTE1 to report problems.