OMAHA, Neb. — Katie Ledecky has set the bar so high, it’s a disappointment when she doesn’t set a world record.

But she has no complaints. She’s returning to the Olympics.

Getting that formality out of the way in her first event of the U.S. swimming trials, Ledecky held off a persistent challenge from Leah Smith to win the 400-meter freestyle Monday night.

“The last 150, I just kept telling myself, ‘Rio! Rio! Rio!'” said Ledecky, who is also a big favorite in two other freestyle races to come. “I just tried to keep myself fired up and didn’t really care what the time was.”

Ledecky, 19, who surprisingly won her first Olympic gold at age 15 in London, is now recognized as one of the most dominant freestylers in history. She set a blistering pace over the first half of the race, putting her more than 2 seconds ahead of the time from her record-setting performance at the 2014 Pan Pacific Championships in Australia.

But Ledecky tired over the final 200, another world mark slipping away when she touched in 3 minutes, 58.98 seconds. Smith pushed Ledecky all the way, also claiming an Olympic berth by finishing at 4:00.65.

The crowd of more than 14,000 groaned when they saw Ledecky’s time, but it was still the third-fastest in history.

“That’s fast,” Ledecky said. “That’s 3 seconds faster than anybody else in the world. I think we’re going to really represent the U.S. well in that event.”

Also, Dana Vollmer locked up another trip to the Olympics less than 16 months after giving birth to her first child.

She finished second in the 100 butterfly behind Olympic rookie Kelsi Worrell, one of several young swimmers already signaling a changing of the guard in the first two days of the meet.

Smith will head to her first Olympics. Ditto for the top two in the 100 breast stroke, won by Kevin Cordes ahead of Cody Miller.

That means seven Olympic first-timers have made the U.S. team. Chase Kalisz, Jay Litherland and Maya DiRado qualified on the first night of the trials.

“Watching the other first-time Olympians, I feel like not a lot of people see the background,” Smith said. “Maya DiRado and Kevin Cordes have been good since 2013 and missed out earlier. I was nowhere near making the team in 2012, it’s been steady progress.”

In the 100 fly, Vollmer, the defending Olympic champion, led at the turn, but the late-blooming Worrell rallied on the return lap to post the second-best time in the world this year at 56.48.Vollmer touched next in 57.21 for the second Olympic spot.

One night after stunningly missing out on an Olympic berth in the 400 individual medley, an ailing Ryan Lochte swam two more grueling races to qualify for Tuesday night’s final of the 200 freestyle.

RIO DE JANEIRO’S acting governor warned that the Olympic Games could be a “big failure,” because of budget shortfalls that threaten to compromise security and mobility during the games.

Francisco Dornelles said the state is still awaiting a $860 million payout from the federal government aimed at shoring up state coffers ahead of the Aug. 5-21 event. Dornelles warned that without them, police patrols may grind to a halt by the end of the week for lack of gas money.

“How are people going to feel protected in a city without security?” Dornelles said. “We can have a great Olympics but if some steps aren’t taken, it can be a big failure.”