Here are five takeaways from the Hawkeye State's summer draw, less than six months before voters will head to Iowa's caucuses.
As his helicopter whirred overhead, children taking free rides aboard it, the real estate mogul was mobbed from the moment he stepped onto the Iowa State Fairgrounds -- more like a reality television star than a Republican presidential candidate. Trump obliged the onlookers, glad-handing those who could squeeze through his thick security cordon, and he did little to discourage shouts like "kick Hillary's ass."
It's his celebrity outsider appeal -- he needs nothing, so he owes no favors -- that's been one explanation for Trump's rise in the GOP polls. But it's the fact that his fans come from well outside the political establishment that could prove to be his biggest challenge.
Only a small fraction of Iowa's registered voters typically participate in its caucuses -- and participants are usually deeply partisan.
Trump's Iowa strategist, Chuck Laudner, told CNN that Trump is casting "a wide net" and has been turning people onto politics who have ignored previous elections. It will fall on the shoulders of Laudner and his organizers to ensure those enthusiasts actually turn up on caucus night.
2. Clinton follows the Iowa playbook, even bringing a tour guide
Where Trump threw out the rulebook, Hillary Clinton
followed it to the letter -- spending more than an hour doing the kind of retail politicking she was faulted for skipping in her failed 2008 bid for the Democratic nomination.
She saw the sights (think Butter Cow). She shook hands and talked to fair-goers. She waited in line for a pork chop on a stick and lemonade. She even brought a tour guide: former Sen. Tom Harkin, still a popular figure in Iowa politics.
It was another clear demonstration that Clinton's lessons from 2008 were about the dangers of taking a lead for granted.
But she and Trump did have something in common: an aversion to risk. They were the two candidates to skip on the fair's toughest stage, the Des Moines Register's Soapbox -- where candidates make their case and take questions from crowds that can number into the hundreds.
3. Bernie Sanders and Donald Trump supporters have a lot in common
Clinton's tour of the fairgrounds was a spectacle, but Trump's raucous, roving mosh pit -- featuring helicopter fly-overs -- was on an entirely different level. But Vermont Sen. Bernie Sanders
trumped them both, drawing hundreds and hundreds to his appearance on the Soapbox, with the crowd spilling across Grand Avenue, the fair's main thoroughfare, and clogging up the midway for non-political passers-by.
The Sanders crowd was far more liberal, but many of its members had a lot in common with Trump's onlookers. They're frustrated. They detest the political establishment. They're sick of money's influence in politics: Sanders eschews it, and Trump says he's so rich he doesn't need it.
"He's kind of right, and he does have a point with that -- the fact that money basically does run politics these days," Laura Hoffman, a 32-year-old nurse's aide in Washington, Iowa, said of Trump.
4. Ben Carson's appeal: Trump on decaf
He often looks bored in debates and television interviews. But on the stump, retired neurosurgeon and GOP candidate Ben Carson
Sanders' Saturday crowd was the biggest, but Carson's Sunday Soapbox draw was close. He riled up onlookers with tales of his medical work and a no-handouts personal story -- and he did it without taking the sorts of personal shots that strike even some anti-establishment Republicans as out of bounds when they come from Trump.
Trump "just doesn't seem to get along with people as well as Ben Carson does," said Alex Bennett, an 18-year-old soon-to-be freshman at Drake University in Des Moines who plans to support Carson in Iowa's caucuses.
Carson has rocketed to second place in both national and Iowa-specific Republican polls, and his outsider bona fides could position him to benefit if Trump falters.
5. Quality time with the underdogs
Though it may have looked that way from the national news, Trump, Clinton and Sanders weren't the only presidential contenders at the fair on Saturday. Former Pennsylvania Sen. Rick Santorum
was there, too, and he slipped into the crowd without quite the entourage.
Santorum started the day speaking on the Soapbox and pressed on at the Iowa Pork Producers' tent, where he flipped pork chops and chatted with voters. One would never know that Santorum had won the Republican caucuses in this state four years ago as he walked through the fairgrounds uninhibited.
It's not all bad for a candidate who made his mark last cycle as an underdog who put in the legwork, getting personalized face time with small groups of voters. It's the sort of retail politicking that a candidate like Trump -- who is mobbed at every step he takes -- couldn't do, even if he wanted to.