Political experts say the phenomenon of “early” voting has changed the dynamics of modern campaigns.

“It used to be you just kind of let the electorate do what they were going to do if you were a campaign. We’d find out Election Day,” says Ann Selzer, president of the company that conducts the “Iowa Poll” for The Des Moines Register. “Well, now they’ve found out If we can get all of these early ballots out there, if we can get people to a poll early, we can recruit those people who don’t really care, but they’re going to vote for our candidate — and those votes are now there.”

Both political parties in Iowa are engaged in a battle for those marginal voters who may not be enthusiastic about the two major parties, but can be convinced to vote early. And Chris Larimer, a University of Northern Iowa political science professor, says campaigns are using different strategies to reach different voters.

“Campaigns are certainly getting more sophisticated in their use of the state voter file in terms of finding likely voters,” Larimer says. “They’re also making campaigns a bit more personal because they know that a more personal touch — and that can be done through direct mail, but it has to be done carefully — can also have an effect on the campaigns.”

Drake University political science professor Art Sanders says in this early voting phase, the campaigns are focused on finding “unlikely” voters.

“Campaigns love early voting,” Sanders says. “It allows them to tailor strategies in much more sophisticated ways. It’s very effective from their perspective.”

Sanders, Larimer and Selzer made their comments during taping of the “Iowa Press” program which airs tonight at 7:30 on Iowa Public Television.

Early voting in Iowa began on September 25. Campaigns are telling voters if they cast their ballots early, they’ll stop getting campaign calls and mailings. Prospective voters for Republican U.S. Senate candidate Joni Ernst are also being invited to participate in telephone conference calls with rising stars in the GOP who encourage early voting. Today First Lady Michelle Obama is campaigning in Des Moines with Bruce Braley, the Democratic candidate for the U.S. Senate, for a get-out-the-vote rally.