Four years ago, a group of prominent Iowans flew on a private plane to New Jersey to try persuading Chris Christie that he should run for president. He didn’t feel the moment was right.

Four years later, despite a rocky campaign year and daunting Iowa odds, the same group is rallying behind Christie again. On Tuesday, they will endorse him at a press conference in Des Moines.

Ahead of the event, Christie told The Washington Post that he plans to begin spending a lot more time on the ground ahead of the caucuses and predicted he'd build a competitive organization.

“It’s an affirmation of our candidacy for all those people who were doubters both here in Iowa and around the country,” he said in a telephone interview Monday evening. “Now with a field that is twice the size as it was then, they’ve taken a good look around at everyone else and they’ve decided to come to me. That’s a real affirmation of the campaign we’re running. These are the difference makers in Iowa.”

The group endorsing Christie is led by agribusiness millionaire Bruce Rastetter, who chartered the plane in 2011. He’s president of the Board of Regents for the state’s public university system, as well as a top donor and close ally to Republican Gov. Terry Branstad.

These are meaningful endorsements for Christie partly because of the men’s closeness to Branstad, a much-admired figure in what might be called the establishment wing of the Republican Party.

“We believe Gov. Christie is a similar kind of governor,” Rastetter said in a phone interview. “He’s a guy that isn’t shy and doesn’t back away from hard decisions.”

Branstad is neutral, but Christie now has managers of the Iowa governor's previous campaigns, a former chief of staff and his top two fundraisers working on his effort. Phil Valenziano, a New Jersey native who was Branstad’s political director in 2014, is Christie’s Iowa state director.

“We’re putting together a winning organization,” Christie said. “Iowa is so dependent on organization … I think we’re going to be very competitive.”

“I don’t know what you call Branstad’s wing,” he added. “I call it the winning wing! If that’s a wing of the party, that’s a wing I want to belong to. The guy has never lost an election here, either a primary or a general.”

Christie traveled several times to Iowa as chairman of the Republican Governors Association last year, spending seven figures to help Branstad’s reelection, which was never really in doubt.

Branstad has said that he does not plan to endorse anyone before the caucuses. He has also said that he prefers candidates who have gubernatorial experience.

The two first candidates to drop out, Rick Perry and Scott Walker, both fit that bill.

The decision by the Wisconsin governor to drop out of the race has prompted both Ohio Gov. John Kasich and Christie to flirt more seriously with a hard play for caucus voters there.

Christie suggested that Walker’s exit gives him an opening in Iowa.

“We have the lane to ourselves as the governor who took on the unions and did it first,” he said, noting that he battled public employee unions before Walker even took office. "Unlike anyone else in this race, I’ve had to deal with a Democratic legislature my entire time as governor.”

Christie bragged about passing tenure and pension reform, while cutting spending and taxes. He also notes that he has vetoed over 400 bills, the most in New Jersey history.

Asked why they backed him, Rastetter praised Christie's plans on entitlement reform and “very practical, commonsense approach to immigration.”

“My thought process has been similar, frankly, to what we were thinking in 2011, when the country needed someone who was a bold, very direct leader who had accomplished things,” he added. “Since that time, the country is more in need of that leadership. We took our time — I certainly did — and looked at the field” before settling on Christie.

The others who will endorse Christie on Tuesday are Denny Elwell, chairman of a commercial real estate company in Ankeny; Gary Kirke, chairman of the Wild Rose Casino and Resort; Mike Richards, vice chairman of the board of directors for Wild Rose; Mikel Derby, currently the legislative liaison for the Iowa Department of Transportation; and Jim Kersten, a former Iowa state senator who worked on Branstad’s staff and is currently vice president of external relations for Iowa Central Community College.

The only one who will not appear with Christie, retired insurance executive Cameron Sutton, is staying neutral because he took a job working for freshman Republican Sen. Joni Ernst.

Rastetter said Christie has a path to victory in the splintered caucuses.

“This race is a marathon, not a sprint,” he said. “You have already seen Walker drop out. You have seen others pull back. Of the governors who have led, I think he’ll continue to rise. As people turn away from the non-conventional, non-traditional candidates, they’ll look for someone who knows how to fix Washington, how to make it work.”

Christie, currently on his ninth trip to Iowa of the year, has primarily focused on New Hampshire’s open primary. But he said he’ll spend more time traveling the Hawkeye State now that autumn has arrived. Iowa kicks off the nominating process on Feb. 1, followed by the Granite State a week later.

Right now, near the bottom of public polls in the state -- he has averaged between 1 and 2 percent in recent surveys -- Christie's supporters there say he benefits from low expectations. But he is also a savvy political strategist who understands the risks that come with playing too hard in Iowa. Unlike a primary, the presidential caucuses require a more considerable time commitment to participate and tend to draw very conservative activists. Those voters are not Christie’s base.

Christie has looked to manage expectations, telling The Post that he was not promising a win in the state and declining to forecast how he might fare.

“We’re going to compete real hard,” he said. “I’m not predicting a victory. The thing is still in flux. We intend to compete and compete hard and do well.”

Rastetter organized an agriculture summit earlier this year that drew all the leading candidates at the time. Christie stressed that any other candidates running would have loved his support. Many of them have come to an invitation-only barbecue that Rastetter puts on every summer.

Reflecting on his current standing in the polls, Christie said Tuesday is “a really important day for us” and noted that Iowa has a tendency to elevate candidates very late in the process. He said he reviewed exit polls from the last two cycles, and more than two-thirds of the voters in both Iowa and New Hampshire said that they made their decision in the last week before voting.

“It’s a long way from people really starting to focus and decide,” he said. “They’re still very much in the shopping mode. I’m not anxious …. We just finished week three of the NFL season. We’ve got to go through the entire regular season and playoffs.”

The caucuses are Feb 1. The Super Bowl is Feb. 7.

“That’s perspective,” he said.