– The moment Gwen Jorgensen took off, her husband could feel what was coming. Patrick Lemieux had been nervously watching her during the 10-kilometer run that ended the Olympic triathlon on Saturday, with defending gold medalist Nicola Spirig Hug on her heels and the rest of the field in their dust.

The two had been locked in a strategic battle until Jorgensen, the best triathlon runner on the planet, decided to end it.

“She knew she was just going to swing the hammer once,” Lemieux said. “When she went, it was one meter [ahead]. Three meters. Six meters. Twenty seconds. And you’re thinking, ‘It’s happening.’ ”

When she crossed the finish line at Copacabana Beach, Jorgensen, of St. Paul, got what she had spent four years pursuing: a gold medal at the Rio Games. She sprinted away from Spirig Hug to win by 40 seconds, finishing in one hour, 56 minutes, 16 seconds. Spirig Hug, of Switzerland, took silver, and Great Britain’s Vicky Holland finished another five seconds back for bronze.

From the time Jorgensen finished 38th in triathlon at the 2012 London Games, she had built her entire life around chasing gold in Rio. She quit a job she loved, left most of her family to train overseas for nine months a year and pushed herself in ways she never thought possible. As she ran the final meters on Saturday, she put her hands to her face in wonderment, then burst into tears as she hit the tape.

Jorgensen became the first U.S. triathlete to win an Olympic gold medal, and she is only the second to win a Summer Games medal of any color. She also is the first reigning women’s world champion to win Olympic gold.

“I’ve been pretty vocal about my goals the past four years,” said Jorgensen, a Wisconsin native who has lived in St. Paul since 2012. “After London, I said ‘I want to go to Rio,’ and I wanted to win gold. Anyone who’s been around me knows how much Patrick has invested, and also [coach] Jamie Turner.

“I was just thinking about all the investments they put into me, thinking about the four years, and it all came down to one day. To be able to actually execute on that day is pretty amazing.”

Devastating run for rivals

Jorgensen won the race in what has become her signature fashion: by dropping her rivals with her devastating run. She was in 23rd place after the 1,500-meter ocean swim, then moved up through the lead pack on the 38.5-kilometer bike race and was fourth when the final leg began.

Early in the run, she and Spirig Hug broke away from the rest of the lead group of about 18 athletes. They spent three laps running into a headwind — with Jorgensen striding out in front, then sometimes giving way to Spirig Hug — and even debated which one should take a lead that neither wanted.

Just after the bell rang to signal the final lap, Jorgensen swung her hammer — and that was that. She ran the 10K in 34:09, after swimming in an ocean current and grinding her way around an eight-lap bike course with a particularly cruel hill.

“To watch Gwen in full flight, usually from behind, is quite something,” said Holland, who had the back seat view again Saturday. “It’s almost inevitable. I’ve seen it in so many races.

“When Gwen is gone, it’s very hard to get her back again. And on the most important day and the most important stage, Gwen did it today.”

For the past two years, Jorgensen has dominated the World Triathlon Union women’s circuit, winning back-to-back world championships. That made her the Olympic favorite months ago, but she didn’t carry any psychic burdens into the race.

She won a test event on the Rio course last summer, which gave her a spot in the Olympics. Turner’s training plan was engineered specifically for what Jorgensen would experience Saturday, including lots of uphill cycling. She felt far less nervous than she did in Rio last summer, because she had been rehearsing for this day for the past year.

Rallying after swim

Just down the beach from a lazy Saturday crowd of sunbathers, Jorgensen sprinted out of the water 12 seconds behind leader Mari Rabie of South Africa. The bike race wound through shady side streets, canyons of Copacabana high-rise condos and along the Atlantica Avenue beachfront. Fans hugged the barriers along the course and packed the bars along Copacabana’s promenade, hollering for their favorite athletes.

Lemieux said that Jorgensen’s swim was below average but that her first lap on the bike was a defining moment in the race. Her powerful climb up a hill that wrecked others erased her rivals’ advantage, and a strong finish on the bike put her in position to bury them with the run.

“When she exited the water, she was [23rd], and there were some real strong legs in front of her,” Lemieux said. “Her competition knows they’ve got one or two critical moments to put Gwen on the ropes. She knew that was coming. And that’s why she’s the Olympic champion.”

Spirig Hug wasn’t finished, however. One of the fittest athletes in the field, she tried to wear her opponents down with a fast bike leg. She and Jorgensen began their chess match then, and it continued during the run, after the two had put 23 seconds between themselves and the rest of the field.

“I was prepared for her to run very well,” Spirig Hug said. “I tried to stick with her as long as I could, and we had some mental games. I tried everything to get her out of the rhythm, to make it hard for her. But she was just too good.”

Failure wasn’t an option

After the race, Lemieux said Jorgensen would have considered a silver or bronze medal a failure. Once Turner told her in October 2012 that she was capable of winning Olympic gold, nothing else would measure up.

Asked if she would be back to defend her title at the 2020 Games in Tokyo, Jorgensen laughed. She is a planner by nature, but she hasn’t given a thought to anything that lay beyond Saturday.

“I’ve said for four years this was my goal,” she said. “On Aug. 20, I wanted to cross that line and get a gold medal. It’s pretty incredible that I was actually able to do it.’’