Former Miss Universe Alicia Machado just became Donald Trump's nightmare

In the past 12 hours, Alicia Machado, an actress, activist and former Miss Universe, has become the kind of character witness with the potential to seriously damage Donald J. Trump's campaign for the presidency.

Machado's decades-old experience with Trump, who once owned the Miss Universe pageant, became the surprise revelation of Monday's presidential debate when Hillary Clinton raised it as evidence of Trump's sexism.

SEE ALSO: Hillary Clinton walks world’s thinnest tightrope in debate with Donald Trump

Now Machado, who is from Venezuela, is speaking publicly about how Trump treated her in 1996 — and why she's campaigning for Clinton. In August, Machado became a U.S. citizen specifically to vote against Trump, though she notes that she supports Clinton and would like to see the first woman president.

Speaking by phone to reporters on Tuesday afternoon, Machado compared Trump's candidacy to a nightmare.

"It’s a really bad dream for me."

"I never thought and never imagined that 20 years later I would be in this position," she said. "It’s a really bad dream for me."

Trump may indeed regret that Machado is playing a pivotal role in the final weeks of the election.

As a Latina immigrant belittled by Trump, voters may become sympathetic toward her and less tolerant of his boorish behavior. All while charges that Trump is insensitive at best and racist and sexist at worst become increasingly difficult to combat in the face of compelling personal stories like Machado's.

The episode is also a reminder that Trump finds it difficult to restrain his impulses, even when the target of his disdain is a relatively private citizen.

In a Fox & Friendsinterview Tuesday morning, Trump discussed Machado unprompted, focusing on the fact that she'd gained weight after winning the Miss Universe crown.

"She was the worst we ever had. The worst. She was impossible," Trump said. "She was the winner and she gained a massive amount of weight and it was a real problem."

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It wasn't long before at least one pundit saw a parallel between Machado and Khizr Khan, the Muslim-American father who criticized Trump at the Democratic National Convention and was repeatedly attacked by the presidential candidate as a result.

"She was the winner and she gained a massive amount of weight and it was a real problem."

"During the closing moments of Monday night’s debate, Clinton provided another Khan moment, and Trump, once again, could not help but reveal his own ugliness," wrote Jonathan Chait.

Machado's surreal role in the election became clear as she watched the debate with her mother and daughter. She'd recorded a video for the Clinton campaign describing Trump's verbal abuse, but Machado had not expected to hear her name on national television.

Toward the end of the debate, Clinton used an opening to point out Trump's long history of dissecting a woman's looks.

"[O]ne of the worst things he said was about a woman in a beauty contest," explained Clinton. "He loves beauty contests, supporting them and hanging around them. And he called this woman 'Miss Piggy.' Then he called her 'Miss Housekeeping,' because she was Latina."

In a rebuke to Trump, Clinton said her name: Alicia Machado.

The campaign then swiftly released a video of Machado describing how Trump's verbal abuse led her to develop eating disorders.

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"I wouldn't eat, and would still see myself as fat, because a powerful man had said so," Machado said.

On Tuesday, Machado emphasized that she's since moved on from her Miss Universe experience, becoming an actress, mother, businesswoman and activist.

"My story can open eyes for this election, that is what I’m trying to do," she said. "Share something I think is important — my experience with this person ... maybe can help to have the best president we need to have."

The impact of her story is already apparent; the day's headlines have been dominated by negative coverage of Trump's behavior even as he aggressively tries to focus on what he's portrayed as a debate victory.

Machado, however, seems to have no intention of letting up.

"I’m here, I’m strong," she said. "I will be here 'til the end and support Hillary Clinton."