In the final week before the 2012 election, all evidence suggests that the presidential race between President Obama and Mitt Romney is locked in a dead heat, with both candidates within striking distance of victory in nearly every battleground state. Which man ends up behind the Oval Office desk come January could plausibly come down to a handful of votes in Ohio, Florida, Virginia, or nearly any other of the several states deemed toss-ups this year. Amid this environment, various state election officials have reported multiple complaints of bogus phone calls, fraudulent letters, intimidation efforts, and threatening billboards all over the country -- including in several of these critical battleground states.

Below, CBSNews.com rounds up a handful of the alleged voter suppression and intimidation efforts many believe are threatening to disenfranchise thousands of people on Election Day.

Bogus mailings, phone calls

For months, both Mr. Obama and Romney have furiously campaigned in the delegate-rich Sunshine State in ongoing efforts to win over the state's diverse collection of voters and pump up turnout ahead of Election Day. But according to the Florida Department of State, some voters there are being targeted with fraudulent efforts attempting to keep them home from the polls.

Chris Cate, communications director of the Florida Department of State, tells CBS News that between 50 and 100 Floridians in at least 28 counties have recently received letters informing them that their citizenship and right to vote is in question. The letters, which are printed on false letterhead from election supervisor Kathy Dent, calls on recipients to return voter eligibility forms to the local Supervisor of Elections office within 15 days of receipt. "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 reads.

Cate says the letters appear to be landing all over the state and that there's no indication it's being sent to areas that trend particularly Democratic or Republican. But he says that while Democrats and independent voters have gotten them as well, a "significant majority" of recipients are Republicans.

The FBI has joined with Florida law enforcement to investigate the letters - which appear to be postmarked from Seattle - but so far, the Florida Department of State says it knows very little about their provenance.

"The number one thing we can do right now is try to get the message out that this is a fraudulent letter and that it's not real," said Cate. "I think the message goes beyond this letter - that Floridians need to be aware that this is the time of year when you're going to see people trying to illegally influencing an election."

The letters aren't the only example of suspicious activity in Florida: Cate said a handful of voters have also received calls informing them that they will be able to vote over the phone - which, he points out, is "not true whatsoever."