You can't listen to an Iowa radio station -- or listen to music on Pandora or watch sitcoms on Hulu -- without hearing a "vote early" plea. Both parties and a slew of special interest groups have been urging Iowans not to wait until Tuesday to cast their ballots. And as of Saturday, more than 30 percent of registered voters had done so.

About two-thirds of Iowa's 3 million residents are registered voters. During the 2008 election, about 1.5 million people voted. The Secretary of State's office reported on Saturday that it has received a historic 640,248 ballots -- 205,697 from registered Republicans, 270,796 from registered Democrats, 162,953 from independents and 802 other ballots. At that point, there were more than 80,000 outstanding absentee ballots. The office plans to release another tally on Tuesday morning, according to a spokesman. 

At this point, the campaigns of President Obama and Mitt Romney seem to be fully focused on making sure that their voters are not stopped by anything as they head to the polls -- not the weather, a work conflict, a sick child or a broken down car. Iowa residents said their phones rang all weekend with out-of-area numbers connected to friendly voices wanting to know why they had not yet voted.  

Dianne G. Bystrom, director of the Carrie Chapman Catt Center for Women and Politics at Iowa State University, said she is a registered independent and she received at least 10 calls on Sunday. She didn't pick up any out-of-area numbers or those appearing to come from research groups, but she did answer a call from a Des Moines area code that turned out to be an Obama campaign volunteer who asked pointed questions about when, where and how she and her husband would vote -- and why they had not voted early.

"They're actually following up with people who have said they will vote to make sure they did," she said. "I think they are going to be calling people up to the last minute tomorrow because I think it's going to be that close of an election."