A billboard with the giant visage of Republican presidential candidate Donald Trump in the back yard of George Davey's home in West Des Moines, Iowa. (Charles Ommanney/The Washington Post)

As Republican front-runner Donald Trump arrived in Iowa this weekend for a final burst of campaigning ahead of the Monday caucuses, he did so in his usual over-the-top fashion: rolling his jet to a stop in front of an airport hangar filled with supporters in this eastern Iowa river town.

The arrival — set to the theme song from the movie “Air Force One” — captured the surreal theatrics that have defined Trump’s candidacy, attracting attention in a way that prompts many to ask: “Is this for real? Is he for real?”

In any other election year, with any other candidate, Trump’s consistently high poll numbers and massive rally crowds would earn him the title of presumed nominee. But this year is unlike any other and Trump is unlike any other GOP candidate — a thrice-married billionaire real estate developer who has never held elected office, wears white shoes to the Iowa State Fair, curses at his rallies and gives rides to children in his Trump-emblazoned helicopter.

Yet Trump is on the cusp of something historic: A candidate who has broken nearly every rule of traditional campaigning is favored to win the Iowa caucuses and several primary contests to follow. The prospect has continued to baffle political pundits, strategists and party leaders, many of whom don’t seem to want to believe what is happening until they see some proof. The Monday caucuses provide Trump with the opportunity to provide some.

“It’s very frustrating because if anybody had the numbers and the turnout and the support that Donald Trump has, I don’t think the media would have any problem saying the normal stuff — that he’s a shoo-in,” said Ted Hacker, 39, who lives in Dubuque and started a trucking company with his wife a year ago. He plans to caucus for the first time on Monday, casting his vote for Trump in hopes of proving that the candidate’s supporters aren’t just fans looking to be entertained. “It’s very frustrating.”

The private Boeing 757 jet owned by Republican front-runner Trump taxis next to a crowd during a campaign rally at Dubuque Regional Airport. (Andrew Harrer/Bloomberg)

After landing in Iowa, Trump held three rallies Saturday in eastern Iowa and two Sunday in the western part of the state, with two more planned for Monday. A poll released by the Des Moines Register and Bloomberg Politics on Saturday showed Trump in the lead with 28 percent of likely Republican caucus-goers saying they will vote for him, compared with 23 percent who would pick Sen. Ted Cruz of Texas and 15 percent for Sen. Marco Rubio of Florida. On Sunday morning, Trump fired off a round of attack tweets before the sun had come up in Iowa, then was interviewed on three of the five major morning talk shows and went to church with his wife.

His message to Iowans throughout the weekend: You have to caucus.

“Unless I win, I will consider this a big, fat, beautiful — and, by the way, very expensive — waste of time,” Trump said of his historic candidacy during a 35-minute speech at an airport hangar here on Saturday. “I really believe that, just a waste of time. So you’ve got to get out and caucus. You have to get out there.”

A year ago, the Republican field was crowded with politicians battling over which camp was better prepared for the White House — governors who had run a state or senators who had worked in Washington. This was supposed to be the election that allowed the Republican Party to reinvent itself, attracting a broader diversity of voters and shifting away from divisive issues.

Trump was everything the party didn’t think it wanted, with his plans for mass deportation and a “great, great wall” on the U.S.-Mexico border. But he seemed to be exactly what many Republican voters wanted: an outsider who has never held elected office and is pumping his own money into his presidential campaign rather than relying on a super PAC. He wasn’t afraid to attack the Republican establishment, his GOP rivals or Democratic front-runner Hillary Clinton. Plus, he made debates fun to watch.

Trump speaks to guests during a campaign rally at Clinton Middle School in Clinton, Iowa. (Charles Ommanney/The Washington Post)

“He’s got everybody stirred up, and that’s a good thing,” said Vickie Hagen, 57, a school bus driver who lives in Davenport and went to Trump’s last event on Saturday. She plans to caucus for the first time Monday, voting for Trump so that he can win her state and prove his doubters wrong. “He’s an anomaly, so it’s like: Let’s find out if he’s really real. I know he can do what he does. He’s a great businessman.”

As Trump tweeted, attacked and gained in the polls, he grew increasingly frustrated that the media and the party were not taking him seriously. At the third Republican debate in Colorado in late October, moderator John Harwood of CNBC listed off some of Trump’s more outlandish promises — building the border wall and forcing Mexico to pay for it, deporting 11 million people and cutting taxes by $10 trillion without adding to the debt.

“Is this a comic book version of a presidential campaign?” Harwood asked.

As the debate audience laughed, Trump responded curtly: “No, not a comic book, and it’s not a very nicely asked question the way you say that.”

Since then, Trump has had to continue to answer such questions, especially after he went on a 95-minute-long, deeply personal rant about one of his rivals, retired surgeon Ben Carson, during a town hall in Iowa. And after he stumbled through questions about whether or not he would set up a database to track Muslims. And after he called for a temporary ban on allowing nearly all foreign Muslims into the country.

And again, just last week, when he skipped the last GOP debate before the caucuses.

“A lot of people have laughed at me over the years,” Trump said at a rally in New Hampshire on Friday, the morning after the debate. “But they’re not laughing at me anymore.”