On the eve of the first huge wave of mail ballots being sent to Florida voters, Democrats filed a federal lawsuit Monday against Gov. Rick Scott's chief elections official, challenging a law that results in thousands of ballots being discarded each election.

The Florida Democratic Party (FDP) and the Democratic National Committee sought an injunction in U.S. District Court in Tallahassee to prevent county canvassing boards from rejecting ballots in cases where the signature of a voter on the mail ballot envelope does not match the same voter's signature on file.

The lawsuit noted that state law has a "cure" mechanism for voters who forget to put a signature on a mail ballot. They can return a signed affidavit to their county elections office confirming their identity. But no such cure exists for cases known as mismatched signatures. Hundreds of them were invalidated across the state in the Aug. 30 primary for that reason, and the number likely will be much larger in November because millions more people will be voting.

"Florida's policy of failing to provide voters an opportunity to cure alleged signature defects on vote-by-mail ballots directly harms FDP, its members, and constituents," the lawsuit states. "FDP is directly harmed because Democratic voters are more likely than Republican voters to have their vote denied due to an apparent signature mismatch. Accordingly, it is more likely that Democratic voters will not have their vote counted, thereby, decreasing the overall likelihood that FDP will be successful in its efforts to help elect Democratic candidates to public office."

The lawsuit was filed against Secretary of State Ken Detzner, the state's chief elections official. His spokeswoman, Meredith Beatrice, said the office could not comment and that she could not confirm that the lawsuit had been served Monday evening.

Detzner's office has a voter outreach program called "Get Ready. Get Set. Vote!" that includes links to the state Division of Elections, which explains the "cure" provision for missing signatures.

"If you forgot to sign your certificate with the returned vote-by-mail ballot, you may still have the opportunity to correct the omission by completing and returning an Omitted Signature Affidavit for Vote-by-Mail Ballot (DS–DE 139 - English PDF / Español PDF) with a copy of your identification," the site says. "The deadline to submit the affidavit, however, is no later than 5 p.m. on the day before the election. Failure to follow the instructions carefully may cause your ballot not to count."

The state web site offers no explanation for those voters whose signatures do not match. However, many counties encourage voters to update their signatures before they vote by submitting a new voter registration application.

Some voters' signatures change because of age or due to an injury. Some voters wrote a cursive signature on a voter registration form but sign a mail ballot envelope in block letters. And in some cases, the signature on the ballot envelope simply is not legible.

"It is important to have your updated signature in our voter file," says the web site of Pinellas Supervisor of Elections Deborah Clark. "This is the signature on file that must match your signature on a mail ballot certificate envelope in order to count your ballot." The solution to the problem, Clark's office says, is for the voter to submit a new voter registration application.

More participating voters cast ballots by mail in Pinellas than in any other county in Florida. In the statewide primary on Aug. 30, the county rejected 203 of the 486 ballots that were presented to the three-member canvassing board for review. Of those 203 lost votes, 53 were rejected for "signature variation," and 88 were thrown out because of no signature.

The Democrats' lawsuit, filed by Washington, D.C. attorney Marc Elias, comes as the party is urging as many voters as possible to cast their ballots by mail. Many Florida Democrats have received letters signed by President Barack Obama, in which he writes: "In Florida, voting is easier than ever because now you can vote by mail. It's the fastest and most convenient way to make your voice heard."

County supervisors of election can begin shipping mail ballots on Tuesday, Oct. 4, and they can begin reviewing them for compliance with the law on Monday, Oct. 24. "Many voters have already received vote-by-mail ballots," the suit claims, and for that reason, Democrats want a judge to issue an emergency order giving voters with mismatched signatures a chance to fix the problem before the election.

"The public interest weighs strongly in favor of letting every lawful, eligible voter exercise the right to vote," the suit states.