(CBS News) Election Day is November 6, but voting for president began today in South Dakota. It's one of 34 states and the District of Columbia that have early voting.
In Florida, half the votes are expected to be cast before Election Day. In Colorado, 80 percent may vote early.
Iowa is the first battleground state where early voting will take place. The printing presses are working overtime to supply ballots to voters requesting them. Iowans can begin casting these ballots by mail or in person on Sept. 27.
"I have to tell you, Iowa, early voting starts in a week," Republican vice presidential candidate Paul Ryan said.
"Get engaged! Get engaged so you can start to vote early!" Vice President Joe Biden said.
Nationally, the percentage of early voters has increased from 16 percent in 2000 to 33 percent in 2008. This year, the number could go as high as 40 percent.
"Any time you have up to 40 percent of your electorate casting a vote before Election Day, it changes the way you communicate with voters," Matt Strawn, former chairman of the Iowa Republican Party, said.
"Sir, would you be interested in voting early in this election?" a Romney volunteer asks a potential voter over the phone.
At a Republican field office near Des Moines, Strawn says early voting helps campaigns improve their focus.
"Anybody that tells one of our volunteers that they're supporting Mitt Romney, you bet we want that vote cast as soon as possible to make sure we can start working on those other Iowans who haven't made their decision yet," he said.
Democrats are following a similar strategy.
"Are you guys planning on voting early in this election?" a volunteer for President Barack Obama's campaign said over the phone to a potential voter.
Sue Dvorsky, who chairs the Iowa State Democrats, believes it helps streamline their message to the people in the middle.
"I think that's the functional and practical result from it," she said.
Dvorsky believes "all the signs point" to voter turnout being higher than 2008.
As of today in Iowa, 103,200 Democrats requested early vote ballots compared to 17,282 Republicans, but early voting is not always a great guide.
Back in 2004, John Kerry had more early votes in Iowa than George W. Bush, but Bush wound up winning the state by 10,000 votes when they were all added up.