Heading into the second presidential debate, Donald Trump and his allies have signalled that he will bring up a variety of claims concerning the sexual behaviour of former president Bill Clinton. Clinton has acknowledged being unfaithful during his marriage to Hillary Clinton but has denied charges of sexual assault.

Trump may also raise a rape case that Hillary Clinton handled as a young lawyer in Arkansas, as well as claim that she attacked Bill Clinton's accusers.

Here's a quick guide to the allegations.

Allegations of an unwanted sexual encounter

Paula Jones -

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A former Arkansas state employee who alleged that in 1991 Clinton, while governor, propositioned her and exposed himself. She later filed a sexual harassment suit, and it was during a deposition in that suit that Clinton initially denied having sexual relations with Monica Lewinsky, a White House intern. Clinton was impeached by the House of Representatives over the Lewinsky matter but acquitted in the Senate. The Paula Jones case itself had been dismissed by a federal judge, who ruled that even if her allegations were true, such "boorish and offensive" behaviour would not be severe enough to constitute sexual harassment under the law. That ruling was under appeal when Clinton in 1998 settled the suit for $850,000, with no apology or admission of guilt. All but $200,000 was directed to pay legal fees.

Juanita Broaddrick - The nursing home administrator emerged after the impeachment trial to allege that Clinton had raped her 21 years earlier. (She originally declined to cooperate with the independent prosecutor, saying in a signed affidavit that "I do not have any information to offer regarding a nonconsensual or unwelcome sexual advance by Mr. Clinton.") Through a lawyer, Clinton denied the claim. There were no witnesses to alleged 1978 encounter, but several of her friends backed her claim. No charges were ever brought. Broaddrick also claims that just weeks after the incident, Hillary Clinton approached her at a political rally and appeared to thank her for her silence.

Kathleen Willey - The former White House aide said Clinton groped her in his office in 1993, on the same day that her husband, facing embezzlement charges, died in an apparent suicide. (During a deposition in the Paula Jones matter, Willey initially said she had no recollection about whether Clinton kissed her and insisted he did not fondle her.) Clinton denied he assaulted her; an independent prosecutor concluded that "there is insufficient evidence to prove to a jury beyond a reasonable doubt that President Clinton's testimony regarding Kathleen Willey was false."

No court of law ever found Clinton guilty of the accusations.

Peter Baker, in "The Breach," the definitive account of the impeachment saga, reported that House investigators later found in the files of the independent prosecutor that Jones' attorneys had collected the names of 21 women who they suspected had had sexual relationships with Clinton. Baker described the files as "wild allegations, sometimes based on nothing more than hearsay claims of third-party witnesses." But there were some allegations (page 138) that suggested unwelcome advances:

"One woman was alleged to have been asked by Clinton to give him oral sex in a car while he was the state attorney general (a claim she denied). A former Arkansas state employee said that during a presentation, then-Governor Clinton walked behind her and rubbed his pelvis up against her repeatedly. A woman identified as a third cousin of Clinton's supposedly told her drug counselor during treatment in Arkansas that she was abused by Clinton when she was baby-sitting at the Governor's Mansion in Little Rock."

Post-presidential travel

After leaving office, Bill Clinton was occasionally a passenger on aircraft owned by convicted pedophile Jeffrey Epstein. (Epstein was also a regular visitor to Donald Trump's Mar-a-Lago estate in Florida, and Trump was a dinner guest at Epstein's home.) Gawker reported that flight logs show that Clinton, among others, traveled through Africa in 2002 on a jet with "an actress in softcore porn movies whose name appears in Epstein's address book under an entry for 'massages.'" Chauntae Davies, the actress, declined to discuss why she was on the flight. Clinton has not commented.

Consensual affairs

Gennifer Flowers -

a model and actress whose claims of a long-term affair nearly wrecked Clinton's first run for the presidency, in 1992. (Clinton denied her claims at the time, but under oath in 1998 he acknowledged a sexual encounter with her.)

Monica Lewinsky - intern at the White House, whose affair with Clinton fueled impeachment charges. This was a consensual affair, in which Lewinsky was an eager participant; she was 22 when the affair started and Clinton, 49, was her boss.

Dolly Kyle Browning - a high school friend who said in a sworn declaration that she had had a 22-year off-and-on sexual relationship with Clinton.

Elizabeth Ward Gracen - a former Miss America who said she had a one-night stand with Clinton while he was governor - and she was married. She went public to specifically deny reports that he had forced himself on her.

Myra Belle "Sally" Miller - the 1958 Miss Arkansas who said in 1992 that she had had an affair with Clinton in 1983. She claimed that she had been warned by a Democratic Party official not to go public: "They knew that I went jogging by myself and he couldn't guarantee what would happen to my pretty little legs."

Some might argue that because Lewinsky and Gracen had relations when Clinton was in a position of executive authority, Clinton engaged in sexual harassment. Certainly an Equal Employment Opportunity Commission claim could have been filed, though these women did not take that opportunity.

Hillary Clinton 'laughed' about a rape case

This refers to a 41-year-old case that resurfaced when the Washington Free Beacon in 2014 discovered unpublished audio recordings from the mid-1980s of Hillary Clinton being interviewed by Arkansas reporter Roy Reed for an article that was never published. The case was also covered extensively in a 2008 article by Glenn Thrush in Newsday.

In 1975, Clinton - then Hillary Rodham - was a 27-year-old law professor running a legal aid clinic in the University of Arkansas in Fayetteville. After a 41-year-old factory worker was accused of raping a 12-year-old girl, he asked the judge to replace his male court-appoined attorney with a female one. The judge went through the list of a half-dozen women practicing law in the county and picked Clinton.

On the recording, Clinton describes it as a "terrible case" and "fascinating." In her autobiography, "Living History," she wrote, "I told (prosecutor) Mahlon (Gibson) I really don't feel comfortable taking on such a client, but Mahlon gently reminded me that I couldn't very well refuse the judge's request."

Ultimately, the prosecution's case fell apart for a number of reasons, including investigators mishandling evidence of bloody underwear, so in a plea agreement the charges were reduced from first-degree rape to unlawful fondling of a minor under the age of 14. Until the Newsday report, the victim did not realize that Clinton had been the lawyer on the other side. She has since attacked Clinton for putting "me through hell."

In the recorded interview, Clinton is heard laughing or giggling four times when discussing the case with unusual candor; the reporter is also heard laughing, and sometimes Clinton is responding to him.

Here are the four instances:

• "Of course he (the defendant) claimed he didn't (rape). All this stuff. He took a lie detector test. I had him take a polygraph, which he passed, which forever destroyed my faith in polygraphs." (Both Clinton and the reporter laugh.)

• "So I got an order to see the evidence and the prosecutor didn't want me to see the evidence. I had to go to Maupin Cummings (the judge) and convince Maupin that yes indeed I had a right to see the evidence before it was presented. (Clinton laughs lightly between "evidence" and "before.")

• "I handed it (a biography of her expert witness) to Mahlon Gibson, and I said, 'Well this guy's ready to come up from New York to prevent this miscarriage of justice.'" (Clinton laughs, as does the reporter.)

• "So (Judge) Maupin had to, you know, under law he was supposed to determine whether the plea was factually supported. Maupin asked me to leave the room while he examined my client so that he could find out if it was factually supported. I said 'Judge I can't leave the room I'm his lawyer!' he said 'I know but I don't want to talk about this in front of you.'" (Reporter says, "Oh God, really?" And they both laugh.)

Clinton's recollections may strike some listeners as callous or cynical about the legal process, especially because she implies her client was guilty.

Hillary Clinton attacked sexual harassment victims

Hillary Clinton has long been a defender of her husband. Carl Bernstein's 2008 book "A Woman in Charge" says that Hillary Clinton was involved in a pre-1992 effort to obtain signed statements from women denying they had affairs with Clinton, including Flowers. "There can be no question that Hillary was Bill's fiercest defender in preventing his other women from causing trouble," Bernstein wrote.

But her opponents have said that Hillary Clinton has gone too far in defending her husband, specifically on the "Today" show on Jan. 27, 1998, a week after the president was accused of having an affair with Lewinsky.

"I mean, look at the very people who are involved in this, they have popped up in other settings," Clinton told Matt Lauer. "This is the great story here, for anybody willing to find it and write about it and explain it, is this vast right-wing conspiracy that has been conspiring against my husband since the day he announced for president."

This is a famous statement by Hillary Clinton, which came after she referenced what she believed were false attacks by Republican foes: "Having seen so many of these accusations come and go, having seen people profit, you know, like Jerry Falwell, with videos, accusing my husband of committing murder, of drug running, seeing some of the things that are written and said about him, my attitude is, you know, we've been there before, we have seen this before, and I am just going to wait patiently until the truth comes out."

This interview, by many accounts, was certainly pivotal to saving Bill Clinton's presidency, as his wife forcefully backed him. But although some describe this as a political attack on Monica Lewinsky and Paula Jones, by Hillary Clinton's account, at the time her husband had not yet admitted the Lewinsky affair to her. That did not happen until Aug. 15, 1998, according to her memoir:

"He told me for the first time that the situation was much more serious than he had previously acknowledged. He now realized he would have to testify that there had been an inappropriate intimacy. ... I could hardly breathe. Gulping for air, I started crying and yelling at him ... I couldn't believe what I was hearing. Up until now I only thought that he'd been foolish for paying attention to the young woman and was convinced that he was being railroaded. I couldn't believe he would do anything to endanger our marriage and our family. I was dumbfounded, heartbroken and outraged that I'd believed him at all."

Moreover, at the time of the interview, Lewinsky also denied there had been a relationship. Her attorney had submitted an affidavit on Jan. 12 from her saying she "never had a sexual relationship with the president." Lewinsky did not begin to testify before the independent prosecutor about the full extent of the relationship until July 27, six months after the "Today" interview. Lewinsky testified for 15 days, after which the president finally confessed to his wife.

When Clinton ran for the Senate, she was asked during a debate whether she misled Americans during the Lauer interview two years earlier. "Obviously I didn't mislead anyone," Clinton replied. "I didn't know the truth. And there's a great deal of pain associated with that and my husband has certainly acknowledged that and made it clear that he did mislead the country as well as his family."