RIO DE JANEIRO β There were no missteps this time β no falls, no stumbles, no alarming moments of insecurity.Mo Farah of Britain, who had tripped on the Olympic track twice in the past week, won the 5,000 on Saturday night with a sure-footed show of confidence, cunning and blistering late speed.
It was a vintage, imperial performance from the 33-year-old: Starting the race at the very rear of the group, he picked off his competitors, one by one, over the course of 12 1/2 laps and surged across the finish line, well clear of the pack, in 13 minutes 3.30 seconds.
The win put him in impressive company: He became the first man in 40 years to win gold medals in the 5,000 and 10,000-meter races in two separate Olympic Games.
Behind him on the track, though, there was considerable confusion. Paul Chelimo of the United States crossed the finish line second and was well into his flag-carrying celebration when he was told, on live TV, that he had been disqualified. Bernard Lagat, 41, who crossed the finish line fourth, moved up to bronze. But that didnβt stand for long.
Later Saturday night, upon even further review, Chelimo was reinstated. He won silver and Hagos Gebrhiwet of Ethiopia took the bronze β knocking Lagat back down to fourth.
Track and field officials did not provide an immediate explanation for the disqualification or the reinstatement.
Farah, who won gold in the 5,000 and 10,000 at the 2012 Games in London, had performed as well as expected in Rio de Janeiro heading into Saturday night, but he had to endure some nervous moments in his earlier races.
Running in the 10,000 a week ago, Farah stumbled toward the track after getting tangled with Galen Rupp of the United States, his friend and training partner, in the 10th lap of the race. Nevertheless, he finished in 27 minutes 5.17 seconds to win the third gold medal of his career.
On Wednesday, in his 5,000-meter heat, Farah tripped again when he collided with Hassan Mead of the United States with about 150 meters left to go in the race. Farah regained his balance and finished in second to safely qualify for the final.
On Saturday night, there was no such awkwardness. Farah slunk to the back of the pack at the beginning of the race, and began gradually working his way up after one lap.
After four laps, he was cruising in middle of the pack. About 3,000 meters into the race, Farah crept all the way to the head of the group, and he fought off every challenger the rest of the way.
Farah, who is known for his long strides and late sprinting ability, ran his final lap in 52.83 seconds. He crossed the finish line with his arms spread out wide, and soon after he dropped to his knees to kiss the track.
Farah is coached by Alberto Salazar, who runs the prominent Nike Oregon Project. Salazar is under investigation by the United States Anti-Doping Agency. He and his athletes have emphatically denied any ties to performance-enhancing drugs.
Entering the race, it was not clear whom Farah would need to fight off. In a big surprise, Kenya β which had won medals in the 5,000 meters in the past three Olympics β did not qualify any runners for the final.
Gebrhiwet was one of three Ethiopians in the race who seemed capable of at least threatening Farahβs dominance. Lagat won medals in 2000 and 2004 in the 1,500, but he seemed like an unlikely podium finisher in this race.
The outcome of the race never seemed to be in doubt. Farah, who moved from Somalia to Britain when he was 8, has been invincible in the last five years. He lost only one 5,000-meter race since 2011, when he moved to Oregon to work with coach Alberto Salazar: the 2013 Prefontaine Classic in Eugene, Ore., which he ran while battling a stomach virus.
It has been reasonable to wonder, given Farahβs age, if his form might begin to show some decline. But there was no sign of that on Saturday.
nytimes.com