David Sorensen, who worked closely with senior policy adviser Stephen Miller, abruptly resigned after he found out that the Washington Post was working on a story about claims his ex-wife had made.
The White House learned about the allegations against Sorensen on Thursday night, according to Raj Shah.
"We immediately confronted the staffer, he denied the allegation and he resigned today," Shah said in a statement.
Rob Porter is one of several alleged abusers Trump has defended
Sorensen, who's in his mid-30s, vehemently denied his ex-wife's accusations, countering that she was actually the abuser.
"In fact, I was the victim of repeated physical violence during our marriage, not her," Sorensen said in a statement, adding that he's "considering legal options to address her defamation."
Sorensen claimed he decided to resign because he didn't want to cause a distraction for the President.
Rep. Patrick Meehan, a Republican leader of the fight against sexual harassment in Congress, was pulled from the House Ethics Committee Saturday, January 20, 2018, amid allegations that he used taxpayer money to settle a sexual harassment claim.
Politicians accused of sexual harassment or assault
Sorensen's resignation comes just two days after staff secretary Rob Porter stepped down amid claims that he physically abused two of his ex-wives. Porter also denied all wrongdoing, but the FBI and senior White House officials knew about the allegations for months, raising questions about why he was allowed to stay on.
Trump applauds Rob Porter's White House work after abuse claims
Sorensen's ex-wife, Jessica Corbett, first contacted the Washington Post last week, telling a reporter that Sorensen regularly abused her during their tumultuous two-year marriage.
Corbett recounted in disturbing detail how Sorensen once ran a car over her foot, put out a cigarette on her hand, shoved her into a wall and grabbed her by her hair while they were on board a boat off the coast of Maine — an incident that had her fearing for her life.
Sorensen joined the White House last May after serving as a senior adviser to Maine Gov. Paul LePage. As a speechwriter on Trump's environmental quality council, Sorensen didn't need a security clearance. White House officials said his background check was still ongoing as of Friday night.
Corbett said she divulged her disturbing abuse claims to FBI agents last October, as part of his background check process.
Corbett called it "scary" that a person like Sorensen was allowed to remain in the White House after what she had told the FBI.
Sorensen claimed he decided to resign because he didn't want to cause a distraction for President Trump.
"Everyone can think you're the most wonderful guy, but you're throwing women into walls by night," she said.
After one particularly violent episode in the fall of 2015, Corbett texted her mother: "He's killing me."
The couple finalized their divorce in September.
Corbett pushed back against Sorensen's claim that she was the abusive one, maintaining that she only occasionally slapped him.
"Everything I told you is 100 percent true and that is why he had to resign today," she said.
Sorensen's sudden departure comes hours after Trump staunchly defended Porter — even though his ex-wife produced a picture of her battered and swollen face after one of his alleged beatings.
"He did a very good job when he was in the White House," said Trump — who's himself accused of sexually assaulting or harassing at least 19 women. “He also as you probably know, says he is innocent and I think you have to remember that. He said very strongly yesterday that he is innocent."