But that's where the similarities end. In contrast to 2016, when Trump was out-organized by rival Senator Ted Cruz and lost the first Republican presidential nominating contest in Iowa, he has established a much-more sophisticated ground game aimed at hoovering up and analyzing voter data to turn it into votes.

The stakes are high: If Trump takes the state in the Jan. 15 contest in convincing fashion, it would fuel the narrative that he is all but assured the 2024 Republican presidential nomination.

Reuters interviews with nearly 40 party leaders, Trump staff and campaign volunteers in Iowa show how the former president has learned from his past mistakes. In 2016, Trump, thinking he had little chance of winning Iowa, kept his operation in the state threadbare. That cost him, even though he would go on to win the party nomination and the presidency.

"I don't think people realize in 2016 how shoestring that was," said Jeff Kaufmann, chairman of the Iowa Republican Party, referring to the Trump campaign. "If you compare 2016 to currently, it has at least five or six times the ground game."

On Sunday Trump will hold a rally in Sioux City, his eighth Iowa event in a little over a month. More than simply building enthusiasm for the candidate, the well-attended rallies are used to identify voters and volunteers and start communicating with them.

As supporters enter Trump rallies they are met with giant screens messaging the time and date of the caucuses and how to find their precinct, while warm-up speakers stress the need to vote, said Rachel Paine Caufield, a political science professor at Drake University who has attended Trump events in the state.

"Because the Iowa caucuses consist of more than 1,600 local party meetings spread out across the state, this kind of organizational list-building goes a long way," she said, referring to the series of meetings in school cafeterias and community centers across the state where voters will choose their party's nominee on Jan. 15.

Trump's nearest rival for the nomination, Florida Governor Ron Desantis, has built a much larger operation, reinforced by out-of-state volunteers who flooded in over the summer to knock on doors. Similar to Cruz in 2016, DeSantis is criss-crossing Iowa to try and run up the score in rural areas, while Trump is focused on population centers home to two-thirds of the vote.

Alex Latcham, early-state coordinator for Trump, said Trump's campaign has a distinct advantage over DeSantis and other Republican hopefuls in being able to mine voter information from rallies he held in the state since his 2016 campaign, as well as from donations received from Iowans over the years and visitors to his website.

"If they've donated to the president, but have never caucused before, then we know they are a supporter and have to turn them out," he said. "It's a mix of all those interactions and touch points that we've had with supporters here."

PLEDGING TO VOTE

Ann Jones is the ideal catch. Wearing a "Don't blame me, I voted for Trump" T-shirt, the 40-year-old gave her information to volunteers at the entrance to a Trump event in Adel, a small town west of Des Moines, on Oct. 16.

Jones, who works part-time at a hospital, said she has never caucused before. Now she is planning to volunteer for the campaign and take her husband, who also has not participated in the caucus before, to their precinct on Jan. 15.

Critically, the campaign now has her contact information. In 2016 Trump didn't have the staffing or digital infrastructure to follow up on such leads, meaning many Trump supporters like Jones and her husband stayed home on caucus night.

"That was an issue back in '16," Marshall Moreau, the campaign's state director, told a recent training session for voting precinct captains observed by Reuters. "That is not a mistake that we're making at all. We're going to over-communicate again, again and again until we're blue in the face."

Following an afternoon rally in Clive, Iowa, last week, staff returned to the campaign's non-descript headquarters just outside Des Moines to input the latest batch of caucus pledge cards into a database. The goal is to make follow-up contact within 48 hours via texts, emails and phone calls.

The 37,500 caucus pledges gathered to date are part of an expansive data operation that has turned out 1,800 volunteers and enough captains, who are tasked with rounding up voters in their area and asked to give a speech in support of Trump on caucus day, for 1,050 precincts. The campaign aims eventually to cover nearly all the roughly 1,700 precincts across the state.

The numbers may not be as large as those disclosed by Never Back Down, a political action committee which says it has recruited nearly 20,000 volunteers for DeSantis, but the Trump campaign believes it is enlisting a more passionate group -- who, importantly, are residents of the Hawkeye State.

One of those volunteers for Trump is Cris Christenson, a business owner who was among the 18 men and women who attended the precinct captain training on a recent Sunday night.

"DeSantis sees a path and he's got the money," said Christenson, seeking to rally his fellow volunteers. "You all need to get motivated ... we need to give it our all."

The DeSantis campaign has relocated one-third of its staff – about two dozen people - to Iowa and has committed to a $2 million TV ad buy to run through the caucuses, banking on the first nominating contest to revive his flagging campaign.

The Florida governor trails Trump by 37 percentage points in the latest Reuters/Ipsos national poll, and is more than 30 points behind in public polling on Iowa.

With a dozen paid staff, Trump has also beefed up its operation in Iowa, recently adding a dedicated person to reach out to pastors and Christian leaders, a key constituency in a state where evangelicals comprised nearly two-thirds of Republican caucus-goers in 2016.

Trump's challengers have targeted evangelicals as a potential vulnerability for the former president, especially after his comments in September disparaging DeSantis' signing of a six-week ban on abortion in Florida as a "terrible mistake."

But so far no issue appears to make a dent in his support.

"Based on godly principles, he loves America. He loves us as individuals," Jonah Jones, 47, said at the Adel rally. "I gotta support my wife, I gotta support my president."