TALLAHASSEE, Fla. (CNS) -- Democrats conceded in the races for U.S. Senate and governor, but not before Florida asked federal authorities to investigate possible election fraud conducted by the party.

The U.S. Department of Justice declined, but the Florida Department of Law Enforcement and the Office of Statewide Prosecution say they have an opened a criminal investigation into the allegations.

Evidence reported to the Department of State suggests a possible effort by Democrats to have voters fix ballots after the state’s deadline in at least four counties.

Cure forms for mail ballots sent to voters by the party show the return date changed from the day before the election to two days afterwards.

Democratic strategist Steve Schale says it was likely just a mix up.

“Some 23-year-old staffer probably got two dates mixed up,” said Schale. “They put the date down for the provisional ballot cure, not the absentee ballot cure, and actually by doing it, all they did was make it harder for their own voters to vote.”

Republicans point to the fact Democrats successfully sued to extend the deadline after the fact.

“It looks like they were just planning on a judge siding with them because of the bias towards trying to allow as many votes as possible to count that were legally cast,” said Eric Eggers, author of the book Fraud. “It's the first evidence we have of systemic efforts to undercut or subvert election law as it was on the book.”

Supervisors of elections who brought the changed forms to the state’s attention say even if it was just a mix up, official elections forms should never have been altered.

“I think the question it raises is what other efforts were underway to subvert election law that we don't know about yet,” said Eggers.

The Florida Democratic Party says it’s hired its own independent investigator to look into the case. It says it plans to release any findings once the investigation is complete.