It was a classic case of going from the outhouse to the penthouse.

Less than an hour before her semifinal at U.S. track trials, 400-meter runner Kendall Ellis was trapped in a porta-potty, banging on the door, screaming for someone to let her out.

Thankfully, somebody did. She won that race in a personal-best time, then came back Sunday to top that mark and win the final, along with the national championship and the spot in the Olympics that comes with it.

“Crazy things happen right before something great is about to occur, so maybe I needed that to get all the nerves and adrenaline out,” she said.

Nobody saw that coming.

Nobody could’ve seen this performance coming, either.

Ellis’ time of 49.81 seconds in the semifinal Saturday marked her first personal best in six years. In the final, she bettered that by .35.

Now, the 28-year-old who was considered mainly a relay specialist will go to the Olympics to compete for a title all her own.

“Just believing in myself,” she said when asked what sparked this sudden resurgence. “The workouts haven’t changed, the results in practice haven’t changed, but finally something clicked up here that said, ‘You can do it. You can go out with the best of them and you can finish better than anyone else.’”

Funny thing is, for the past six years, she’s had the video to prove it.

Even today, if you type some combination of the words “greatest” “track” and “comebacks” into the browser Ellis’ video from the 2018 NCAA championships will come up somewhere high on the first screen.

In that race, Ellis made up 30 meters over the homestretch to lead Southern California to a win in the 4×400 relay.

Halfway through the last lap of that 2018 relay, she was in third place, barely in the screen. A few seconds later, the TV announcer all but handed the race to the Purdue runner in the lead: “There’s no way, unless they drop the baton, Purdue’s going to win this, which we certainly didn’t see.”

Ellis had a couple of things going for her. She knew the Purdue runner was a middle-distance specialist without the same closing kick as she has.

“And I wasn’t listening to the announcer or anyone else,” she said. “I’m always going to be optimistic about my chances. I mean, if I don’t believe in me, then who else will?”

The win that made Ellis something of a mini-legend in the track world. She made a number of national teams in part on the strength of her relay prowess. In Tokyo three years ago, she won an Olympic gold by running in the prelims of the women’s 4×400 and also got bronze in the mixed 4×400.

But one memory that sticks from that year was her fourth-place finish at trials — a .07-seconds defeat that left her on the outside looking in on the individual race.

“I remember being so heartbroken,” she said. “I’d have rather gotten fifth place or sixth. But it was certainly a learning lesson, and coming into today, I told myself I did not want that feeling again.”