Gov. Ron DeSantis of Florida has a classic American dream story.

He hardly ever tells it.

A middle-class kid, his baseball skills helped take his team to the Little League World Series — not that many Iowans would know it, despite his visits to all 99 of the state’s counties throughout his campaign for the Republican nomination. After graduating from Harvard Law School, he chose to join the Navy and deployed to Iraq, which he usually mentions only in passing. His wife, Casey DeSantis, was diagnosed with breast cancer early in his governorship, but he almost never talks about what it took to support her through it — while raising three young children — or what he learned.

And although Mr. DeSantis frequently appears with his children on the trail, he is more likely to describe them by their ages (7, 5 and 3) than their names (Madison, Mason and Mamie). Even Ms. DeSantis, a former newscaster who is seen as providing a human touch, tends to call him “the governor” instead of “Ron” at his rallies.

If there were ever a time for Mr. DeSantis to tell more of his bootstrap biography it would be now, as his hopes of a strong finish in the Iowa caucuses, and perhaps his entire presidential campaign, seem to be ebbing away. He trails former President Donald J. Trump by more than 35 points in Iowa and will almost certainly fare worse in New Hampshire on Jan. 23. Former Gov. Nikki Haley of South Carolina has overtaken him in most polls.

But in a speech outside Des Moines on Thursday, just four days before the Iowa caucuses, when Mr. DeSantis invoked Benjamin Franklin and the sacrifices needed to preserve the republic, which included needing to “sometimes put on a uniform,” he didn’t take the opportunity to mention his own service or the fact that he is the lone veteran in the race. He talked about the “biomedical security regime,” ballot harvesting, social credit scores and FICA, but said almost nothing about his family.

Those who know Mr. DeSantis describe him as intensely private, averse to personal braggadocio and more comfortable with policy than with people. He believes deeply that Republican voters do — or should — care about his conservative bona fides and his accomplishments as governor more than his life story and personality. Two former advisers said he has long resisted efforts to persuade him to open up.

Mr. DeSantis’s reluctance to tell his own story has allowed him to be defined by others, especially Mr. Trump, who has cast him as awkward and weak. And it has made him seem bloodless in comparison with Ms. Haley, a daughter of immigrants who folds her life experience into almost every stump speech.

“I don’t mind saying on the record that I’ve pushed him a little bit to not be afraid to tell that story,” Representative Chip Roy of Texas, who has endorsed Mr. DeSantis and campaigned alongside him across Iowa, said during an interview in West Des Moines this week. “Because it’s a good one. But it’s to his credit. It’s just not a part of his DNA to want to trumpet that kind of stuff about himself because it’s never been about him.”

American politics relies as much on storytelling as on policy. Bill Clinton was the Man from Hope. John McCain was a maverick, a war hero who put country first. Barack Obama represented hope and change. Mr. DeSantis’s campaign does not even have a bumper-sticker slogan.

That sense of remove has made itself clear on the campaign trail. His stump speech is about facts, not feelings. When Mr. DeSantis does invoke his life experiences, it can sound more like bullet points he is ticking through on a résumé, rather than moments to which voters might relate.

He frequently says he is the only veteran running; he infrequently tells stories about his time in Iraq or at Guantánamo Bay, or about the service members he served alongside — few of whom have campaigned with him. And when he does speak about enlisting after the terrorist attacks of Sept. 11, he sometimes talks about it not in the usual frame of sacrificing for his nation — but by noting the financial opportunities he bypassed along the way in choosing to forgo a cushy career in corporate law.

Although Mr. DeSantis considered announcing his White House bid at a baseball field in his hometown, Dunedin, Fla., in May, he ultimately chose a far less intimate venue: a livestream Twitter forum with Elon Musk. The event was audio only. Viewers could not even see the face of the man who wanted to be their next president.

“A gifted politician takes a story of their background and weaves it into a narrative about how he or she understands you and your concerns and your challenges and your fears,” said Whit Ayres, a Republican political consultant who worked for Mr. DeSantis during his first run for governor in 2018. “They make an emotional connection with people, and that’s just not part of his skill set.”

A strong personal narrative seems especially crucial for any candidate hoping to dethrone Mr. Trump, who has become a master of his own story, aided by his hit television show “The Apprentice.” Of the remaining contenders, Ms. Haley is most clear about how her biography informs her politics, even finding an opportunity to do so in a 15-minute speech to a trade group for the renewable-fuel industry in Iowa on Thursday.

“The reason I’m running is because my parents came here 50 years ago to an America that was strong and proud and filled with possibilities,” Ms. Haley told the crowd. “I want them to know that country again.”

She went on to cite her husband and his fellow soldiers (“I want them to know their sacrifice matters”); her daughter and son-in-law, who struggled to afford a home (“The American dream is getting away from us”); and her son, a senior in college (“I’m tired of watching him write papers on things he doesn’t believe in just to get an A”).

It’s the type of human connection voters say they would like to hear more of from Mr. DeSantis.

Jessie Eben, 35, who heard Mr. DeSantis speak in Rock Rapids, Iowa, this week, said she already knew plenty about his policies and wanted to see him be “genuine” and talk more about his experiences “as a human being.”

“I think you have to have empathy to be a good leader,” Ms. Eben explained.

Of course, Mr. DeSantis has a host of challenges unrelated to how he presents himself to voters, including the indictments of Mr. Trump, which rallied Republicans around the former president, as well as a messy campaign structure that has generated reams of negative news stories. A good life story is also no antidote for a poor candidate. Senator Tim Scott of South Carolina — who had perhaps the race’s most compelling and often-told biography — dropped out early.

David Polyansky, Mr. DeSantis’s deputy campaign manager, said Iowans had gotten to know Mr. DeSantis through his constant travels around the state.

“The people across the state have had the opportunity to meet him in person and hear him from cafes and diners to town halls,” Mr. Polyansky said. “He’s answered their questions, he’s shaken their hands and he’s taken pictures with them over and over and over.”

But instead of telling his story directly to voters, Mr. DeSantis often allows his wife and his political allies to describe his life when they introduce him at events, especially when it comes to his service as a military lawyer.

“As a Navy guy, I don’t think it’s in his character to go out there and brag,” said Dave Vasquez, a spokesman for Never Back Down, a super PAC supporting Mr. DeSantis.

Earlier in the campaign, Never Back Down produced a series of television ads highlighting Mr. DeSantis’s biography. One explained that he was “the grandson of a steelworker” and mentioned his Bronze Star. Another, entitled “Grit,” talked about how he paid his way through college with blue-collar jobs.

But Mr. DeSantis rarely gets personal in the places where it would seem most natural. His memoir does not recount a conversation with another human being until it reaches his senior year at Yale.

He has also largely avoided talking about the profound tragedies life has brought him — unlike President Biden, who often speaks about what he has learned from grief.

In November, at a gathering of conservative Christians in Iowa, Mr. DeSantis revealed publicly for the first time that his wife experienced a miscarriage earlier in their marriage. He chose not to dwell on the moment, however, calling it a “tough thing” and a test of faith. At a CNN town-hall meeting this month, he was asked to discuss the sudden death of his sister, which he rarely does. He called it the kind of “loss that hits you the most” but showed little outward emotion.

“When they asked about the death of his sister, he walked through it very analytically, but I think that’s kind of who he is,” said Bob Vander Plaats, an influential evangelical leader in Iowa who has endorsed Mr. DeSantis. “There’s no doubt he cares deeply, but he’s not going to wear it on his sleeve.”

Despite his apparent emotional reticence, Mr. DeSantis visibly has more energy when his wife and children are with him at campaign events. When they are absent, he calls his wife or video chats with the kids after almost every campaign stop, five people who know him said.

It’s exactly the kind of authentic, touching detail that his supporters seem to value.

In Le Mars, Iowa, on Thursday, Mr. DeSantis told the crowd that his son had started to parrot some of his best lines from the previous night’s debate against Ms. Haley. The crowd chuckled.

Arlene Lang, 83, said she was glad Mr. DeSantis had indulged in banter that “wasn’t so serious.”

“Everyone listens a little better then,” Ms. Lang said.

Reporting was contributed by Molly Longman from Rock Rapids and Le Mars, Iowa; Shane Goldmacher from Des Moines and Clive, Iowa; and Catie Edmondson from Grimes, Iowa.