TOKYO — Mondo Duplantis was a high school freshman when his life changed.
A pole-vaulting prodigy from Lafayette, La., Duplantis was a couple of months from his first international competition, the 2015 world youth championships, when he received a recruiting call from a coach. The twist was that the coach was from the Swedish Athletics Association.
“He would call me and my parents every day going, ‘You should compete for Sweden, we’re super well-organized, we’re going to take care of your poles, we’re going to do everything for you,’ ” Duplantis recently recalled. “It sounded like a pretty good offer.”
Duplantis has since emerged as one of Sweden’s most beloved athletes, endearing himself to a once-skeptical public by speaking Swedish in interviews, driving Swedish cars, buying a place to live in Sweden during the summer and dating a Swedish model, Desiré Inglander. The two made headlines when they kissed on live TV in early July at a track meet in Stockholm. (Duplantis won.)
“I think today he’s fully embraced,” said Lisa Gunnarsson, 21, a native of Stockholm and one of Duplantis’s training partners. “If I say I pole-vault, people say, ‘Oh, yes, Mondo Duplantis.’”
At the Tokyo Games, where the men’s pole vault final is on Tuesday, Duplantis could see his celebrity soar even higher. Already the world-record holder at age 21, he is the favorite to win his first Olympic title in an event he has dominated the past two years.
“I always thought I had the ability to be the best pole-vaulter in the world,” he said before the start of the Games. “I thought that ever since I was a little kid.”
In many ways, Duplantis fits right in with Sweden’s love of technical events in track and field, said Erik Karlsson, a track and field correspondent for the Aftonbladet newspaper in Stockholm. The country has plenty of indoor and outdoor facilities, and good coaches. The weather is too cold to embrace sprinting, so Sweden has traditionally excelled in events like the high jump and the long jump, along with the discus.
After Swedish athletes dominated the men’s discus here last week, winning gold and silver, Duplantis posted a congratulatory message — in Swedish, of course — on Instagram.
But there was some suspicion and lack of understanding at first about Mondo’s motivation for competing for Sweden, Karlsson said. Many Swedes did not realize that his mother, Helena, a former heptathlete, is Swedish, or that he had the option to do so because he has dual citizenship.
There was also some public hesitancy to accept him because two other high-profile athletes who became naturalized Swedes — Ludmila Engquist, the 1996 Olympic women’s 100-meter hurdling champion who was born in Russia, and Adeba Aregawi, the 2013 world champion in the women’s 1,500 meters who was born in Ethiopia — became involved in doping scandals.
Duplantis acknowledged that he had a practical reason for aligning with Sweden. By doing so, he does not have to qualify for the world championships or for the Olympics by finishing in the top three at a trials competition, as he would if he were representing the United States. One bad day on the runway could have been enough to keep him off the team.
“I think I would be lying if I said in the beginning that it wasn’t a factor,” he said.
In Sweden, Duplantis was not viewed as an opportunist, Gunnarsson said, but “people didn’t understand. He was an American, not a Swede.” In the years since, Duplantis has made an effort to “Swedish-ify himself,” she said, by learning and speaking the language. (“Survival Swedish,” is how Duplantis described his level of proficiency.)
Asked what separates Duplantis from other vaulters, Gunnarsson cited his technique, confidence, the sheer number of jumps he has taken since he began vaulting at age 3 or 4 and the fact that his coach and father, Greg, was an All-American vaulter at Louisiana State.
“You get such a good head start” when you begin jumping that young, said Gunnarsson, who recently won the women’s pole vault while competing for L.S.U. at the N.C.A.A. outdoor championships. “He can jump anytime, anywhere.”
It is Duplantis’s personality, as well as his jumping skill, that has made him popular in Sweden, Karlsson said. In a newspaper poll of 1,500 Swedes last year, he won in a landslide as the country’s most popular athlete, defeating the soccer star Zlatan Ibrahimovic and the three-time Olympic champion cross-country skier Charlotte Kalla.
“Once people learned his story, most of the suspicion vanished,” Karlsson said. “When he started jumping world records, nobody cared anymore.”
Today, Duplantis splits his time between Louisiana and Sweden, where the summers are “magical,” he said. But while he once puttered around in an old Toyota, he now drives Swedish-made automobiles: a Volvo in Louisiana, and a Polestar in Sweden.
“I think I have a really nice balance on the two lives I live right now,” he said. “I have family and friends in both places.”
He also has big goals. He is taking aim at Sergey Bubka, the most legendary figure in the sport, and his collection of accomplishments.
“I want to do more than Bubka’s done, for sure,” Duplantis said. “More Olympics than him, more world championships.”
On a more provincial level, Duplantis has already raised the bar for Swedish vaulters, said Patrik Sjoberg, a retired Swedish high jumper who once held the world record in the event. Sjoberg, who regularly traveled with Swedish vaulters during his career, said they could be finicky.
“They say it’s impossible to jump in bad weather; it’s impossible to jump when it’s raining; it’s impossible if you have a headwind; it’s impossible if you have wind from the left or from the right,” he said. “But Mondo proved, ‘Well, if you don’t want to jump in bad conditions, I’m still going to do it.’”
Other Swedish vaulters “feel a little stupid,” Sjoberg said, now that Duplantis has made a habit of conquering the elements.
In the process, Duplantis has powered past his competition. A crowning achievement could come this week.
“As long as he wins, he’ll be a super-Swede,” Sjoberg said.