Less than four months out from the first caucuses, the two presidential hopefuls have grown into the best of enemies. They are polar opposites who have learned to define themselves by clashing with each other. Trump has heckled Bush since the start of his campaign, and the Florida governor -- who at first seemed hesitant to respond to Trump's attacks head-on -- has been swinging back.
At town halls in New Hampshire last week and dueling campaign stops in Iowa this week, the two men seemed to embrace their respective roles with distinctive campaign styles. As Trump boasted of his "strong tone," Bush said his style was more "Iowa nice" and vowed fix Washington with "civility."
Trump rolled into the small town of Waterloo on Wednesday in a flashy motorcade and a private security detail, thrilling supporters eager to catch a glimpse of the reality-TV-star-turned-presidential-frontrunner. His fiery speech was tailor made to stir up the rowdy crowd — a mix of sweeping promises and dire warnings about a country being constantly attacked and undermined by outsiders.
Bush got celebrity treatment, too -- though of a different kind. As he criss-crossed parts of the state, Iowans reminded him — not always kindly — that two men with his last name have already been in the White House.
Bush spent much of his time answering questions from the audience, on everything from the Syrian refugee crisis to climate change, rather than delivering provocative speeches. In contrast to his rival, Bush emphasized experience over style and optimism over alarm.
"They're polar opposites as people. Donald Trump is a celebrity. Jeb Bush is a very substantive, thoughtful person," said Mark Jacobs, a wealthy energy executive and Bush donor who unsuccessfully ran for Senate in Iowa. "I think as people begin to do a thoughtful analysis and look at Jeb's record, there's more and more people that are going to gravitate to him."
The Iowa swings this week come at a crucial juncture in the 2016 cycle. The large GOP field is starting to winnow, and many donors and voters are looking to soon get behind a candidate who can go the long haul.
Even when they weren't calling out each other by name, the implication from both Bush and Trump was clear: The other guy's not fit to lead this country.
Speaking to supporters in a local ballroom in Waterloo, Trump said that people are sick and tired of the "political-speak," and called on the room to elect someone with a "much tougher, much stronger" tone.
"I have a strong tone. People's heads are being chopped off, we're getting beaten at every front," Trump boomed on stage. "We're losing everywhere!"
Twenty-four hours later, Bush was pleading with Iowans at a pizza joint in Indianola to do just the opposite. Look past the candidates with the "big voices and the grandiose talk," Bush said, and choose substance over personality.
"We can't rely on the loud voices. We can't rely on untested people," Bush told about 200 people packed into a small restaurant. "I believe at the end of this process that people are going to want to know that you're a proven leader."
Each of their messages are reverberating with their bases.
Passionate Trump fans in Iowa said they're fed up with politically correct politicians, want a candidate who can inject a jolt of energy into the party, and they are certainly not interested in a third President Bush. Many of them echoed Trump's alarm about what they perceive to be an America being overtaken by outsiders — from foreigners entering the country illegally to refugees seeking shelter in the United States.
Paul Weber, a 71-year-old veteran from Appleton who attended the Trump rally, said he was horrified about the influx of "new Americans" to the country.
"The people that are coming in here from China, Indonesia and all that countries — they're getting pregnant and coming here and having babies," the self-described "redneck" Trump supporter told CNN, telling an Asian reporter that he meant no offense. "I hope he does put up that fence down there on the border."
In contrast, Bush fans said they're more interested in a candidate with a proven record in public office and want to support someone they can picture sitting behind the desk at the Oval Office.
"He's done a good job in Florida, and I think he would make a good president, maybe even a better president than his brother," Harlan Hirsch, an 84-year-old veteran who lives several miles southwest of Indianola.
Hirsch, who is leaning toward supporting Bush or Rubio, summed up the main difference between Bush and Trump like this: "Bush is probably a little more stable, a little more sound, and a little more presidential."
For now, Bush has quite a bit of catching up to do in Iowa.
Trump continues to lead in the Hawkeye State with 24% support, according to a recent NBC News/Wall Street Journal poll
. Bush is at 7%, behind Ben Carson's 19% and Carly Fiorina's 8%.
Asked about his trailing numbers in the state, Bush's senior adviser Sally Bradshaw echoed how Bush has described his overall 2016 strategy: slow and steady.
"Look, this is a journey. This is a process," Bradshaw said. "His numbers have slowly continued to improve as we've gotten our messaging out and people get to know the governor."
Getting the message out is exactly what the Trump campaign is trying to do more of in this state. His unorthodox campaign is showing sure signs of a maturing grassroots operation: outside of the rally in Waterloo, volunteers were collecting contact information from voters on leaflets that on one side listed Trump's platform, and on the other explained how the Iowa caucuses work.
Still, where Bush has boasted about his well-organized and well-funded campaign, Trump seemed eager to prove that he's far from running a typical campaign.
He told CNN afterward addressing the crowd in Waterloo that as important as it is for him to win the state, he has no Iowa-specific campaign strategy.
"You saw the rally inside. It's something very special," Trump said. "There's no strategy. We just want to make America great again. That's my strategy."