Supreme Court Justice Clarence Thomas, shown at College of the Holy Cross in Worcester, Mass., in 2012, said of Moira Smith’s groping allegation: “This claim is preposterous and it never happened.” (Michael Dwyer/AP)

The 25th anniversary of Justice Clarence Thomas’s confirmation to the Supreme Court has featured testimonials from his supporters, a symposium on his jurisprudence and tributes from conservative legal scholars about his influence on the court.

But Thursday brought an unwelcome echo of the sexual harassment allegations that almost derailed his 1991 nomination: An Alaska lawyer told the National Law Journal that Thomas groped her at a dinner party in 1999, when she was a young Truman Foundation scholar in Washington.

Through a court spokeswoman, Thomas told the publication: “This claim is preposterous and it never happened.”

The woman, Moira Smith, said she decided to make the allegations not because of Thomas but because of Donald Trump. She posted the information on her Facebook page on Oct. 7, hours after the media disclosed that Trump had boasted on tape about grabbing women.

“When Justice Thomas touched me inappropriately and without my consent, I was 23 years old — and felt there was nothing I could do,” Smith said in a statement released Wednesday. “Seventeen years later, it is clear that sexual harassment, misconduct and assault continue to be pervasive, having an impact on all women. I choose to speak out now in the hope that this will change.”

Smith said she was helping her boss at the dinner party when the incident occurred. Guests contacted by the National Law Journal said they saw nothing untoward. Smith, who posed for a photo with the justice later that night, did not tell them Thomas had grabbed her buttocks.

But friends said Smith told them about the alleged groping that same night and the next morning, and they were not surprised when Smith again recounted the incident earlier this month.

“I don’t remember the specific timeline,” Amy Hertel Buckley, 39, another Truman scholar at the dinner that night, told The Washington Post. “But when I saw her Facebook post, it was instantly familiar to me. It’s been a long time, but she definitely told me about that after it happened.”

Marcia Coyle, the longtime Supreme Court reporter who wrote the story, said Smith did not come forward. Smith initially made her Facebook posting private so that only friends could see it, Coyle said. Smith made it public after friends told her she should.

A source told Coyle about the posting — Smith’s Facebook account has now been deactivated — and Coyle interviewed her and others who corroborated her account over a two-week period, according to the NLJ report.

The dinner party was held at the Falls Church, Va., home of Louis Blair, then head of the Truman Foundation. It was a scholarship program founded by Congress to identify students “who demonstrate outstanding potential for and who plan to pursue a career in public service.”

Smith, now the vice president and general counsel of Enstar Natural Gas Co. in Alaska, was a resident scholar who assisted Blair. Her unofficial duties involved helping coordinate events such as the dinner, which preceded another event at which Thomas was to give an award named for a judge he knew. Buckley said she also helped out at the dinner.

Smith told the National Law Journal: “I was setting the place to his right when he reached out, sort of cupped his hand around my butt and pulled me pretty close to him. He said, ‘Where are you sitting?’ and gave me a squeeze. I said, ‘I’m sitting down at the garden table.’ He said, ‘I think you should sit next to me,’ giving me squeezes.”

Smith said she was “so confused about what happened” because she liked Thomas but also felt he “had transgressed such a line.”

The NLJ report said “her three former housemates during the spring and summer of 1999 each said in interviews they remembered Smith describing inappropriate contact by Thomas after she came home that night from the dinner or early the next morning.”

In her Facebook post, Smith said she had been the victim of date rape in college, and also groped by an acquaintance. After hearing the Trump tape, she said, she decided “enough is enough.”

She also told the NLJ: “We now know that many men in power take advantage of vulnerable women. That willingness by men in power to take advantage of vulnerable women relies on an unspoken pact that the women will not speak up about it. Why? Because they are vulnerable. Because they are star-struck. Because they don’t want to be whiners. Because they worry about their career if they do speak out. But silence no longer feels defensible; it feels complicit.”

Thomas’s supporters rallied quickly to his defense, saying the charges were part of an unrelenting attack on the conservative justice. Some tied Smith to Democratic activists and noted that her husband is a former Democratic party official.

“The alleged conduct bears no resemblance to the man I worked closely with, whom I still count a friend after nearly 10 years,” Carrie Severino, a former Thomas clerk, wrote on the National Review website. “Those of us who have known the justice or worked with him in any capacity . . . including those who disagree with him, recognize him to be a good and honest man.”

Mark Paoletta, a former assistant White House counsel who worked on Thomas’s confirmation, questioned the timing. “I do not consider it a coincidence that this Democratic smear on Justice Thomas comes as he celebrates 25 years on the court, and in the heat of a presidential election.”

Severino and Paoletta noted that Smith in the past has supported Democrats, and that a former husband worked in the Obama White House. One of the friends who confirmed Smith’s story is a political consultant who works with Democrats.

In her statement, Smith said she was motivated by her children. “As the mother of a young daughter and son, I am coming forward to show that it is important to stand up for yourself and tell the truth,” she said.

Thomas spoke Wednesday during his remarks at the Heritage Foundation about his own confirmation hearings, marked by the allegations of Anita Hill that he verbally harassed her, and about other confirmation hearings since.

“The city is broken in some ways,” Thomas said, adding, “at some point, we have got to recognize that we’re destroying our institutions.”

Julie Tate contributed to this report.