Convicted felons who want to have their voting rights restored after leaving prison are encountering problems with election officials who don't always interpret requirements correctly, political scientists and prisoner advocates say.

Roadblocks have cropped up most recently in Ohio, Florida and New York state. They result, at least in part, from confusion among election officials over varying state laws and revisions in some of those laws in recent years, said Michael Margolis, a University of Cincinnati political science professor.

"But they're supposed to know the law," he said.

Prisoner advocates have accused Ohio election officials of giving wrong information to released felons seeking to have their voting rights restored. The advocates sued this week, asking a federal judge to compel Ohio's secretary of state and county boards of election to fix the problem before the Oct. 4 deadline for registering to vote in the Nov. 2 presidential election.

If successful, the lawsuit could add thousands of voters in a state already considered a battleground between President Bush and Democrat John Kerry. The lawsuit seeks to represent 7,000 to 21,000 released felons.

For felons already trying to re-enter society under the stigma of being convicts, confusion about whether they are allowed to vote again can impede their efforts to become productive citizens, said Robin Templeton, director of the Right to Vote Campaign. The New York-based civil rights coalition focuses on helping felons regain their voting rights.

"It's not about partisanship and one party or the other trying to get people to vote a certain way," Templeton said. "It's really about democracy and the law being implemented."

States have authority to set qualifications for voters. In their 2002 book, "American Elections: The Rules Matter," political scientists Robert Dudley and Alan Gitelson outlined the contrast in state laws regarding felons and their right to vote.

Fourteen states permanently forbid convicted felons to vote. Thirty-two states prohibit offenders from voting while they remain on parole.

Ohio law requires county elections boards to cancel the voting registration of people convicted of felonies. But another state law says the voting rights must be restored once felons are released from prison, even if they are still on parole or probation.

Despite that, 21 of Ohio's 88 elections boards gave wrong information to testers posing as felons who asked how to register to vote, said David Singleton, a lawyer with the Prison Reform Advocacy Center. Singleton filed the lawsuit Tuesday against Ohio Secretary of State Kenneth Blackwell and county boards of election statewide.

Some boards incorrectly said felons couldn't vote until after they had completed parole, while others said the felons would have to provide documentation to prove they had been released, even though Ohio's law doesn't require that, Singleton said.

Blackwell, Ohio's chief elections officer, says he has been informing election boards about the law on restoring voter rights since it took effect in 1996. He also distributed copies of the Prison Reform Advocacy Center report on the test results to all election boards with a reminder of what state law requires, spokesman Carlo LoParo said.

"We take this very seriously," LoParo said.

State officials are discussing possible short- and long-term solutions, including offering voter registration services in parole offices and having elections board employees use the state prison system's Web site to confirm whether inmates have been released.

A survey two years ago of county elections boards in New York state found problems similar to Ohio's with elections officials asking felons for documentation that wasn't required or that, in some cases, did not exist, said Jessie Allen, a lawyer at the Brennan Center for Justice of the New York University School of Law. Allen supervised two law students who did the survey.

Lee Daghlian, spokesman for the New York State Board of Elections, agreed on Thursday that the documentation request caused problems because various counties handled the situation differently and the requested paperwork wasn't always available.

The problem seems to have been resolved during the past year, though, because New York's boards of election are now using the state prison system's Web site to verify whether prisoners have completed their sentences and probation terms, Daghlian said. New York law requires that felons complete probation before they are allowed to vote, he said.

Daghlian said his state's election officials worked with Allen's group on solving the problem.

Allen is lead counsel in a court fight with Florida over restoring voting rights to felons. As a result of that dispute, Florida's top elections official ordered a review in July of the state's voter database after a list used by county officials to remove thousands of felons from voting rolls was found to contain mistakes. It listed thousands of people who are eligible to vote, Florida officials said.