This year, how Republican candidates come off could hold even more importance than in past years, Dianne Bystrom, director of the Carrie Chapman Catt Center for Women and Politics, told FoxNews.com. In June, the Iowa Republican Party decided to officially scrap its high-profile presidential straw poll which had traditionally served as a test of a candidate's popularity.

How a politician performs in Iowa, the crucial first-in-the-nation caucus state, can light a path to the White House or dash D.C. dreams.

"Talk about your accomplishments," she said. "What have they done and what will they do for Iowa?".

A handful of Democrats, including Vermont Sen. Bernie Sanders, former Maryland Gov. Martin O'Malley, former Virginia Sen. Jim Webb, former Rhode Island Gov. Lincoln Chafee and Democratic National Committee Chairwoman Debbie Wasserman Schultz will also attend.

"It's not a great venue for attacks," she said.

Among the GOP hopefuls vying for viewer attention are Ohio Gov. John Kasich, Wisconsin Gov.Scott Walker, former Florida Gov. Jeb Bush, Florida Sen. Marco Rubio, New Jersey Gov. Chris Christie, Louisiana Gov. Bobby Jindal, former Sen. Rick Santorum, former Arkansas Gov. Mike Huckabee, South Carolina Sen. Lindsey Graham, former Texas Gov. Rick Perry, Texas Sen. Ted Cruz, neurosurgeon Ben Carson, former HP CEO Carly Fiorina and Donald Trump.

Bystrom says candidates who play it positive and cut the controversy out of their 30-minute speeches will make the most impact with voters.

WASHINGTON-- It doesn't get much more American than the Iowa State Fair-- a place where butter is king, hog calling is sport and politicians are tested.

This year, 19 presidential hopefuls from both parties are gearing up to make the annual August pilgrimage, where they'll be personal and up-close with voters like Bob Hemesath.

Former Texas Gov. Rick Perry delivers a speech at the Iowa State Fair in Des Moines, Iowa. (Reuters).

He also wants answers on where they stand on the renewable fuel standard. In May, the Environmental Protection Agency announced changes to how much corn-based ethanol and other biofuels can be mixed into gas and diesel. The new rules could change how Hemesath, like many others in the largely agricultural state, make a living.

It's very open," Hemesath told FoxNews.com. "It's not a campaign stump speech. In May, the Environmental Protection Agency announced changes to how much corn-based ethanol and other biofuels can be mixed into gas and diesel. The new rules could change how Hemesath, like many others in the largely agricultural state, make a living.

This year, the challenge for the 17 Republicans in the running for the 2016 GOP nomination will be to find ways to set themselves apart from the pack. Bystrom says they'll have to do it by striking just the right cord.

The PG-rated tone also means candidates should think carefully before making any big policy statements or weighing in on controversial topics like Planned Parenthood and immigration, Bystrom added.

"What happened to the kinder, gentler Mike Huckabee?" she asked, referring to his performance, which some called caustic, at the first Republican presidential primary debate on Aug. 6.

The fair, home to culinary gems like corn in a cup and fierce face-offs in the beard-growing competition kicks off Thursday in Des Moines and has become a perennial stop for presidential candidates looking to test drive their message and electability.

Hemesath, a farmer from northwest Iowa, says he wants candidates to lay out their priorities and goals for the future of Iowa agriculture.

Hillary Clinton, former secretary of state, is not scheduled to appear.

"It's a very relaxed. It's very open," Hemesath told FoxNews.com. "It's not a campaign stump speech. You have the opportunity to shake their hand. It's a much more open, friendly atmosphere.".

"It's not a great venue for attacks," she said. "It's a family-friendly environment. Set an optimistic tone.".

The event has grown both in popularity and political prominence. In 2002, attendance hit one million and since then, has passed the million mark 11 times.

The Iowa State Fair, first held in 1854, has turned into a venue where voters go for answers.