It's a sign that Election Day is getting closer: increasing reports of efforts to intimidate or mislead voters. Florida officials say they're now investigating fake letters that have been sent to voters in at least 20 counties questioning their citizenship and eligibility to vote.

The letters look official, with an eagle and flag logo at the top. They appear to be signed by the local supervisor of elections, although they're not. (Gannett's in Florida compares the fake letter — on top in this example — to an official letter below from the elections supervisor.)

Each letter tells the recipient that the elections office has received information "bringing into question your eligibility as a registered voter." The letter goes on to say that only U.S. citizens can vote, and that it's a felony to fraudulently register. It asks the voter to return an attached "Voter Eligibility Form" within 15 days or risk being removed from the rolls.

"A nonregistered voter who casts a vote in the State of Florida may be subject to arrest, imprisonment, and/or other criminal sanctions," the letter warns.

Chris Cate, a spokesman for the Florida Department of State, says most of the letters appear to be going to Republicans. He says voters who received one should report it to their local election supervisor or a state voter fraud hotline (1-877-868-3737) so authorities can find out who's behind the mailings. Most of the letters were postmarked in Seattle.

"This is an example of why voters need to be vigilant during the election season and to be aware that there may be people out there committing fraudulent acts," Cate said.

There have been other reports that voters in Florida and Virginia have been receiving phone calls telling them that they can vote over the phone, which they can't.

Every election, similar efforts are made to try to prevent voters from casting ballots, and those behind the schemes are seldom caught. The laws governing voter intimidation are often vague, and not everything that people find intimidating is illegal.

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