Several groups are asking a federal court to block Florida's push to remove potentially ineligible voters from the rolls.
The lawsuit filed in Tampa on Friday says the purge cannot go forward unless it is approved by federal officials. The U.S. Department of Justice has told the state the same thing.
Florida, at the urging of Republican Gov. Rick Scott, began looking for ineligible voters last year. An initial search turned up as many as 182,000 registered voters who may not be U.S. citizens.
Earlier this year state officials sent to local election officials a small list, of more than 2,600 voters, and asked supervisors to start the process to remove them from the rolls. Supervisors have questioned the accuracy of the list.
The challenge comes from two naturalized citizens represented by the American Civil Liberties Union and by a Hispanic civic organization.