ANALYSIS: "All I can say is it's totally fake news. It's just fake. It's fake. It's made-up stuff, and it's disgraceful, what happens, but that happens in the world of politics."

That's what US President Donald Trump says of claims made by at least 16 women who accuse him of sexually harassment.

On Friday (Saturday NZ Time), Jacqueline Alemany, of CBS News, asked for the official White House position on the accusations: "Obviously, sexual harassment has been in the news. At least 16 women accused the president of sexually harassing them throughout the course of the campaign. Last week, during a press conference in the Rose Garden, the president called these accusations 'fake news'. Is the official White House position that all of these women are lying?"

CARLOS BARRIA/REUTERS US President Donald Trump has called sexual harassment allegations made against him "fake news".

White House spokeswoman Sarah Huckabee Sanders responded, saying: "Yeah, we've been clear on that from the beginning, and the president's spoken on it."

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JONATHAN ERNST White House press secretary Sarah Huckabee Sanders says Donald Trump's accusers are lying.

As Alemany noted, 16 women have accused Trump of sexually harassing them. While the US president dismisses this as "fake news", the problem for the White House is that some of these women have produced witnesses who say they heard about the incident at the time - long before Trump made his political aspirations known.

Such contemporaneous accounts are essential to establishing the credibility of the allegation because they reduce the chances that a person is making up a story for political purposes. In the case of sexual allegations, such accounts can help bolster the credibility of the "she said" side of the equation. Often, a sexual assault will happen behind closed doors. The contemporary corroborators can explain what they heard at the time and whether the story being told now is consistent with how the story was told years earlier. This does not necessarily mean the allegation is true, but it does give journalistic organisations more confidence to report on the allegation.

Below is a summary of the corroborators provided by three of the women who have accusations, drawn from a fact-check written during the 2016 US presidential campaign. That fact-check also detailed the witnesses who backed up claims of sexual accusations against former US President Bill Clinton - who, like Trump, insisted the women accusing him were not telling the truth.

Readers can judge for themselves.

KRISTIN ANDERSON

Her allegation: While at a Manhattan nightclub in the early 1990s, Trump slid his fingers under her miniskirt, moved up her inner thigh and touched her vagina through her underwear.

Corroborators:

- Kelly Stedman, a friend. She said she was told about the incident at a women's brunch a few days later. The women found themselves "laughing at how pathetic it was" on Trump's part.

- Brad Trent, a New York photographer. He says he heard the story from Anderson at a dinner in 2007. "It was just girls saying stories about how they got hit on by creepy old guys," Trent said of the conversation around the table.

NATASHA STOYNOFF

Her allegation: While interviewing Trump in 2005 for an article for People magazine about the first anniversary of his third marriage, Trump lured her into a room at Mar-a-Lago and abruptly kissed her, forcing his tongue down her throat. He then said they were going to have an affair.

Corroborators:

- Marina Grasic, who has known Stoynoff for more than 25 years. She said she got a call from her friend the day after the attack, detailing exactly how Trump pushed Stoynoff against a wall.

- Liz McNeil, at the time a reporter for People (she is now an editor). She said that she heard about the incident the day after Stoynoff returned from her assignment. "She was very upset and told me how he shoved her against a wall," she said.

- Mary Green, another People reporter (now editor) who had just returned to New York. "In an early conversation we had in her office, she told me about what happened with Donald Trump," Green said. "She was shaky, sitting at her desk, relaying that, 'He took me to this other room, and when we stepped inside, he pushed me against a wall and stuck his tongue down my throat. Melania was upstairs and could have walked in at any time.'"

- Liza Hamm, part of a "tight-knit' group of friends. "Natasha has always been a vivacious person who wants to believe in the best of people, and this experience definitely messed with that outlook," she said.

- Paul McLaughlin, Stoynoff's former journalism professor. He said Stoynoff called him at the time of the alleged incident seeking advice on how to handle it: "She didn't know what to do, she was very conflicted, she was angry, she was really confused about how to deal with this." After a discussion, he said, Stoynoff decided it would be best if she kept the incident to herself.

RACHEL CROOKS

Her allegation: Trump, in 2005, kissed her directly on the lips after she introduced herself and said she was a receptionist who worked for a company that did business with Trump.

Corroborators:

- Brianne Webb, her sister. She said Crooks called her immediately about the incident as soon as she returned to her desk. "Being from a town of 1600 people, being naive, I was like, 'Are you sure he didn't just miss trying to kiss you on the cheek?' She said, 'No, he kissed me on the mouth.' I was like, 'That is not normal'."

- Clint Hackenburg, her boyfriend at the time. After he asked her that evening how her day had gone, "she paused for a second, and then started hysterically crying".