For those who would be president, a visit to the Iowa State Fair may be the purest distillation of the campaign experience in the state that starts the voting in the race for the White House.

The 10-day event started Thursday and most of the 2016 presidential hopefuls will pass through, pausing to chomp on deep-fried snack foods, visit with locals out for a day of fun and spending some time on the political "soapbox" to talk with voters.

If all goes well, the fair provides an opportunity for candid interaction with voters and shows off a side not often seen on TV. People fondly remember Barack Obama's ride on the bumper cars with his family in 2007.

But in the increasingly stage-managed world of presidential politics, awkward moments and ill-timed soundbites can flow from this unscripted setting.

"It's an important thing for candidates to do," said Tom Henderson, chairman of the Democratic Party in Iowa's Polk County. "The pitfall is that in prior years, the real news story has been hecklers, which leads to quotes the candidates have to answer for."

Consider the case of Mitt Romney, who during the last campaign said atop The Des Moines Register's soapbox: "Corporations are people, my friend." The comment dogged Romney, the former private equity executive, for the rest of his campaign.

This year more than a dozen candidates for president are scheduled take their turn on the soapbox, among them Republicans Jeb Bush, Scott Walker and Marco Rubio. Donald Trump, the real estate developer and former reality TV star, will attend will attend Saturday afternoon, campaign aides told the Register. He has been dominating the Republican presidential race this summer, but is still considered a long-shot candidate for the party's nomination in the 2016 election.

Democrats Bernie Sanders and Martin O'Malley will attend, too. Party front-runner Hillary Rodham Clinton will attend: She's coming to the fair, but hasn't yet said if she'll take a turn on the box.

Iowa is already a place where even the most cautious-minded and carefully managed political candidate can have unexpected intimate " and sometimes just plain weird " moments with the public. At campaign stops in recent months, Bush held hands and prayed with a flower-laden man in a top hat, Walker embraced a sobbing homeless military veteran and Clinton graciously accepted garlic pills from a supporter concerned for her health.

The fair only amplifies the Iowa experience. Will Rogers, Republican chairman of Polk County, called it "the Iowa culture crammed into 10 days."

For Republicans, the cancellation of the traditional Iowa Straw Poll makes the fair an even more important destination. The poll had been a mainstay of the Republican presidential primary since 1979, raising money for the state party and culling the field of candidates. It was a weak predictor of candidate success in Iowa's caucuses, however, and some major candidates skipped it. The Iowa party decided in June to drop the poll.