Democratic presidential candidate Joe Biden faces a sexual assault allegation against him by a former employee.
Tara Reade, who worked for the former US vice-president nearly 30 years ago, says he sexually assaulted her in the halls of Congress.
Mr Biden has been accused of being "touchy feely" by multiple women, but this is the first public accusation of serious sexual misconduct against him.
The White House hopeful has denied the allegations. "I'm saying unequivocally: it never, never happened," he said during a TV interview.
Acquaintances of Ms Reade have said she confided in them after the alleged assault.
With the claim looming during a presidential election year - the first such vote since the emergence of the #MeToo movement - let's take a look at what exactly Mr Biden is accused of and how he has responded.
What is the accusation?
Tara Reade, 56, worked as a staff assistant to Mr Biden from 1992-93 when he was a senator for the US state of Delaware.
In recent interviews, she has said that in 1993 her former boss forced her against a wall and put his hands under her shirt and skirt after she delivered him his gym bag.
"There was no exchange, really, he just had me up against the wall," she said to podcast host Katie Halper in March 2020.
"I remember it happened all at once... his hands were on me and underneath my clothes." He then penetrated her with his fingers, she said.
"I remember him saying, first, as he was doing it 'Do you want to go somewhere else?' and then him saying to me, when I pulled away... he said 'Come on man, I heard you liked me,'" she said.
"That phrase stayed with me."
Ms Reade filed a criminal complaint on 9 April 2020 with police, saying she was a victim of sexual assault but did not name Mr Biden.
She said in a tweet that she filed the complaint "for safety reasons only", as the statute of limitations for her claim had expired and she had begun to receive online threats.
What evidence has emerged?
Ms Reade was one of several women who came forward last year to accuse Mr Biden of inappropriate touching, hugging or kissing, though none, including Ms Reade, described his actions as sexual assault at the time.
Three people have now backed her account of being assaulted, although none say they were witnesses to it. Her brother, a former neighbour and a former colleague have said that they heard her describe the accusation against her boss after the alleged incident.
Lynda LaCasse, who lived next door to Ms Reade after she left Washington in 1993, told Business Insider: "This happened, and I know it did because I remember talking about it."
She recalled Ms Reade crying while describing her experience as they both shared stories of violence in their lives sometime in 1995 or 1996.
"I remember her saying, here was this person that she was working for and she idolised him," Ms LaCasse said.
"I remember the skirt. I remember the fingers," she said. "I remember she was devastated."
"I have to support her just because that's what happened," said Ms LaCasse. She said she felt compelled to support Ms Reade because "we need to stand up and tell the truth." However, she said she still planned to vote for Mr Biden in the November presidential election.
Lorraine Sanchez, a former legislative aide who worked with Ms Reade in the office of a California lawmaker from 1994-96, told Business Insider that, during that time, Ms Reade had described being mistreated by a former boss.
Ms Reade said "she had been sexually harassed by her former boss while she was in DC", according to Ms Sanchez, who added that she could not remember whether Ms Reade detailed the type of harassment, or named Mr Biden.
Meanwhile, Ms Reade's brother, Collin Moulton, told the Washington Post that she had told him in 1993 that Mr Biden had touched her neck and shoulders.
Several days after the interview, he added in a text message that he recalled her telling him that Biden had put his hand "under her clothes", the Post reported.
Ms Reade said a 1993 phone call to CNN host Larry King also provided a contemporaneous account of her claim. Ms Reade said that a woman who called into the show claiming that her daughter left a job in Washington after "problems" with a "prominent senator" was her mother, who died in 2016.
Ms Reade said she had filed a complaint with a congressional personnel office about her treatment as Mr Biden's employee, but did not have a copy of the report. Journalists at the New York Times and Washington Post say they have been unable to locate the report.
Separately, the records of Mr Biden's 36-year career as a US senator are being held at the University of Delaware, which says it will not release any papers until two years after Mr Biden leaves public life.
Ms Reade says the records will contain evidence that she complained to her superiors about Mr Biden, and perhaps that other members of his staff may have made similar accusations.
How has Biden responded?
His campaign said in early April that the alleged incident "absolutely did not happen".
Mr Biden, 78, "firmly believes that women have a right to be heard - and heard respectfully", said his campaign spokeswoman.
"Such claims should also be diligently reviewed by an independent press. What is clear about this claim: It is untrue."
On Friday, Mr Biden issued a statement saying: "Women deserve to be treated with dignity and respect, and when they step forward they should be heard, not silenced."
He added "their stories should be subject to appropriate inquiry and scrutiny", and said journalists should "evaluate the full and growing record of inconsistencies in her story, which has changed repeatedly in both small and big ways".
He also gave his first TV interview on the subject, saying: "The truth matters... it did not happen. Period."
He said he would not release his records at the University of Delaware because the records did not contain personnel information and he feared the contents would be "taken out of context" and used as "fodder in [the presidential] campaign".
No senior aides to Mr Biden say they can recall overhearing a complaint from Ms Reade.
"I have absolutely no knowledge or memory of Ms Reade's accounting of events, which would have left a searing impression on me as a woman professional, and as a manager," Mr Biden's executive assistant Marianne Baker said.
There have been no other allegations of serious assault made against Mr Biden.
In an investigation into Ms Reade's account by the New York Times, two friends said she had described the details of a traumatic sexual attack involving the former vice-president, in 1993 and 2008.
But the newspaper found no corroboration from any former staff members of Mr Biden and found "no pattern of sexual misconduct by Mr Biden".
Will this hurt Biden's presidential bid? Probably not
It's possible that Tara Reade's accusation of sexual assault against Joe Biden could derail his campaign, but it seems unlikely. Here's why.
Americans already know about the "touchy feely-ness" of the former VP and they factored that in as they chose him to be their nominee. He put out a video saying he'd learned from #MeToo that times have changed and that his history of rubbing women's shoulders, kissing their heads, etc, was not appropriate. Evidently, that was seen as apology enough by most primary voters.
An accusation of sexual assault is of course more serious but the criteria for judging whether someone is a sexual abuser is looking at a consistent story from the accuser and a pattern of behaviour in the accused. Ms Reade is so far the only woman to accuse Mr Biden of sexual assault. If no others emerge, Democrats may be inclined to believe their candidate over her.
Joe Biden is running against Donald Trump, who has been accused of sexual misconduct by some 25 women. That may not stop the President using it as an attack line (he's hinted at it before), but it does diminish the credibility of the attack.
In the midst of this pandemic, almost no other news is breaking through. In a normal cycle this story would be getting a lot more attention in newspaper headlines and on cable TV. Today it barely registers. That's helpful for Mr Biden.
The Democratic Party does hold itself to a higher standard on inclusivity of race and gender than the Republican Party does, so this accusation is uncomfortable. But this year, the standard that matters most to Democrats is getting Mr Trump out of the White House. They believe Mr Biden has the best shot at doing that.
Other incidents of touching
Several other women have come forward over the last year to accuse Mr Biden of inappropriate touching, hugging or kissing, though none described his actions as sexual assault.
In response, Mr Biden pledged to be "more mindful" in his interactions.
Ms Reade was among those to speak out last year, saying that he had touched her several times on her shoulder and neck.
In an interview with Nevada newspaper The Union in April 2019, she claimed that her career was sidelined after she refused to serve drinks at an event.
She said Biden had requested that she serve because he liked her legs. She told the paper that she did not feel like the alleged acts toward her were about sex but rather "power and control".
In interviews with the Washington Post last year, she made no mention of the alleged assault, and said she blamed Biden's staff for "bullying" her more than Biden.
"This is what I want to emphasise: It's not him. It's the people around him who keep covering for him," she said at the time.