And he appeared to do it without breaking a sweat or into a smile, breezing through the record heat to win easily in two hours 11 minutes and 12 seconds.
"This," the former UCLA runner said, "was a victory lap for me."
Jared Ward, who finished third in the 2015 L.A. Marathon, grabbed the third Olympic berth in 2:13:00.
Amy Cragg (2:28:20), Desiree Linden (2:28:54) and
The temperature was 66 degrees when the mixed field of 366 runners approached the starting line at Gilbert Lindsay Plaza near Staples Center, making the race the hottest in U.S. trials history. And it would be 12 degrees warmer by the finish.
But Rupp didn't seem to notice, growing stronger the deeper he got into his first marathon.
"In the beginning of the race, I was just trying to conserve as much of my energy as possible," said Rupp, the second man to win the U.S. Olympic trials marathon in his debut at the distance. "I didn't know what to expect those last few miles.
"Everybody I talked to told me it's going to feel easy at the start. But it's going to hit you at some point and it's going to hit you like a ton of bricks."
The bricks never came.
Rupp was running comfortably just off the lead when Tyler Pennel began to push the pace midway through the third of four six-mile loops around the USC campus and Exposition Park. And when Rupp and Keflezighi were the only two runners to cover the move, the crowded pack began to break up.
"Tyler made that race," Keflezighi said.
A short time later it was Pennel who fell off when Rupp lowered the hammer, covering three of the next five miles in 4:47. The final burst, in the 23rd mile, was the one that broke Keflezighi.
While the warm weather didn't seem to bother Rupp, it almost wrecked Flanagan's day.
She and Cragg train together in Portland, Ore., where Rupp also lives, and for most of the race they fed off one another. Dressed identically in sunglasses, white visors and running tops, black Nike shorts and white shoes, they ran side-by-side for the first 24 miles, with Flanagan helping Cragg through a rough patch in the middle of the race when the pair pulled away.
So when Flanagan began to fade, needing more than 12 minutes to cover the 24th and 25th miles, Cragg tried to return the favor.
"I asked her, 'Hey, are you OK? And she was like, 'No, I'm not,'" said Cragg, who noticed Flanagan's face was bright red as the two women approached the final aid station. "There were a couple of times where she [said], 'I'm not sure I can do this.'"
With Linden closing quickly, Cragg eventually had to leave her partner. A mile later, as she approached the finish, she pulled her visor off and waved to the cheering crowd.
She then wrapped an American flag around her shoulders and waited for Flanagan, who staggered across the line and collapsed into her arms before being taken away in a wheelchair.
"I worked so hard the last four years to move up one spot," said Cragg, who actually improved three places after missing the U.S. team by finishing fourth in the 2012 trials.
For Keflezighi, the race and its aftermath proved emotional.
"I had a few issues going on," said Keflezighi, who had cramps early in the race then felt like he was going to throw up in the final miles. He said he was also thinking about a woman he described as his "second mother" who is in failing health and a close friend in Dallas whose infant son recently underwent heart surgery.
"You just draw energy and be the best that you can and dig deep," he said.
Two hours later Keflezighi was brought to tears when his new teammates were asked at the post-race news conference what they thought of the four-time Olympian, at 40 the oldest American to qualify for the Games' marathon.
"Meb is an incredible athlete. And that pales in comparison to how wonderful a person he is," said Cragg, a former training partner.
"Meb," Linden added, "is the epitome of a hero. He's what we strive to be."
Although the biggest prize the runners were chasing was a seat on the U.S. charter flight to Brazil, they also picked up some spending money Saturday, with the winners earning $80,000 each from a record purse of $600,000. Second place was worth $65,000, $10,000 more than third.
But Keflezighi said he felt rich even before they handed him the check.
"I'm more than thrilled to be on the team," he said, breaking into another wide smile. "The fourth time's the charm."
Here's a look back at the race:
11:42 a.m.: Favorites continue to lead
Barring a monumental collapse, the six U.S. entrants in the men's and women's marathon for the Summer Olympics in Rio de Janeiro have been decided with nearly nine miles still to run in Saturday's U.S. trials.
On the women’s side, Portland, Ore., training partners
On the men’s side, Tyler Pennel broke off a 4-minute 47-second 17th mile, towing track star
11:25 a.m.: Flanagan, Cragg out front
Portland, Ore., training partners
Taylor and Hall were more than 50 meters off the lead.
On the men’s side, Tyler Pennel led
11:10 a.m.: Lead packs pull away
The men's field began to string out as the leaders passed through the halfway point of Saturday's U.S. Olympic marathon trials, reaching 13.1 miles in 1 hour 6 minutes 32 seconds.
In the women’s field,
The temperature on the course was 70 degrees, making the race the hottest in U.S. Olympic trials history.
10:55 a.m.: Men's leaders pass 10-mile mark
The men's field in the hottest U.S. Olympic marathon trials in history passed 10 miles in 50 minutes 38 seconds with a large and tightly bunched pack of leaders that included defending champion
Former Mexican Olympian Diego Estrada, who went to high school in Salinas, was also among the leaders.
Temperatures rose 4 degrees from the start, to 70 degrees, during the opening third of the 26.2-mile race.
On the women’s side, training partners
10:35 a.m.: McCandless opens lead in men's race
Tyler McCandless, who recently earned his Ph.D in meteorology from Penn State, has pushed to a five-meter lead in the U.S. Olympic men's marathon trials, towing the field through 10 kilometers in a cautious 31:34.
A pack of about 20 women passed three miles in 17:25. Favorites
10:25 a.m.: Keflezighi, Aciniaga take men's lead
As the men’s field passed the three-mile mark with Fountain Valley’s Nick Arciniaga and three-time Olympian
The men's leaders ran the first mile in 5 minutes 4 seconds and reached two miles in 10:13 and three miles in 15:13.
10:10 a.m.: And they're off …
The men's field in the U.S. Olympic trials marathon dashed away from Gilbert Lindsay Plaza under 61-degree temperatures just after 10:06 a.m. Saturday. The 160 runners will complete a 2.2-mile downtown loop, followed by four flat six-mile loops from the Convention Center to the Coliseum and back.
Temperatures are expected to rise at least 14 degrees during the roughly 2-hour 10-minute race – warm for a marathon, but much cooler than anticipated.
Former UCLA star
The top three men's finishers will become the first track and field athletes to qualify for the 2016 U.S. Olympic team that will compete this summer in Rio de Janeiro.
A field of more than 160 of the nation's best men's marathoners was set to leave Gilbert Lindsay Plaza near the Staples Center just after 10 a.m. Saturday. And when they get back in a little over two hours, the first three across the finish line will win the right to represent the U.S. in this summer's Olympic Games.
The 200-plus runners in the women's field will began their race at 10:22 a.m..
In addition to a berth on the Olympic team, runners in the trials field are also chasing a portion of a record $600,000 in prize money that will pay $80,000 each to the men's and women's winners.
The men’s race is more wide open. Former UCLA star
Many runners said Friday they anticipate challenges from the heat -- which is expected to hit 75 degrees by the finish -- and the four-loop course, which features nearly 90 turns.
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