Jessica Leeds enters her apartment building, Wednesday, Oct. 12, 2016, in New York. Leeds was one of two women who told the New York Times that Republican presidential candidate Donald Trump touched her inappropriately. (AP Photo/Julie Jacobson)

PHILADELPHIA - New allegations have surfaced of sexual assault against Donald Trump — but they are not recent incidents, dating back in one case as much as three decades. That's left some of Trump's supporters and others asking the question: Why now?

The four women who came forward this week cited Sunday night's debate, and Trump's denial of ever kissing or groping a woman without consent, as the straw that broke the camel's back and prompted them to talk with news organizations. One, Jessica Leeds, told The New York Times she "wanted to punch the screen" when she heard Trump's response during the debate.

Critics nevertheless are asking why the women waited so many years to finally speak out, and some are using that as ammunition to question the veracity of their claims. The same question and doubts were raised after dozens of women came forward years after the fact to accuse comedian Bill Cosby of sexual assault.

The Associated Press explored that question and the skepticism surrounding it with experts and accusers in other cases, including Cosby's. Here is their take:

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WHY NOT COME FORWARD SOONER?

"The number one reason (people hesitate) is they are afraid they won't be believed ... because a lot of this happens in private. You may tell friends, because they'll believe you, but you may be afraid to present to authorities. You may have been drinking, or you're afraid of being blamed. You're not even sure if you may be at fault."

— Dr. Judith Linden of Boston University, an emergency room physician who treats sex assault victims.

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WHAT ELSE MIGHT HOLD AN ACCUSER BACK?

"There's never a good time to come forward. If you come forward immediately, you're accused of being a gold digger. If you come forward later, you're accused of being liars. ... You know that when you go forward with a story of sexual assault, especially against a powerful person (or school), you feel isolated, you feel alone. You know you're going to be attacked.

"There's still this misconception that there's something to be gained by being a victim of sexual assault. ... Rehashing a painful moment publicly is not fun, especially when you know that so many people who hear that story are cultured to question you."

— Kamilah Willingham of Los Angeles, whose account of being sexually assaulted at Harvard Law School was featured in the campus sexual-assault documentary "The Hunting Ground" and was the subject of a Title IX discrimination complaint against the school.

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WHAT IS YOUR OWN EXPERIENCE WITH THIS?

"There's a lot of re-victimization. ... I was told that my story was 'decades old, fantastical.' ... It's had a huge impact on my family. ... I've been harassed, chased through grocery store parking lots. Drivers scream at me, flip me the finger. That's pretty embarrassing and hurtful and really difficult."

— Cosby accuser Barbara Bowman, explaining the backlash after she came forward in 2005 to support another woman suing Cosby of sexual assault. She penned a 2014 column in The Washington Post asking why no one believed her accusations earlier, and she is now one of seven accusers suing Cosby for defamation in Massachusetts. Cosby, 79, is defending several civil suits around the country and faces criminal charges in the case of another woman.

(Note: The Associated Press does not typically identify people who say they have been sexually assaulted, but both Willingham and Bowman agreed to be named publicly.)

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IS THERE A SILVER LINING TO ANY OF THIS?

"If there's anything encouraging to say about the last week, and the last couple of years in particular, it's the pendulum swinging. ... It does say something positive about society, that this is not the kind of culture and society we want. ... There is a cost for misogyny."

— Shaunna Thomas of Los Angeles, a co-founder of the online women's rights group UltraViolet Action, which ran a full-page newspaper advertisement this week condemning Trump, signed by 3,000 self-described sexual assault survivors.

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This story has been corrected to remove a quote incorrectly attributed to Sen. Jerry Moran. It has also been corrected to say Willingham's account was the subject of a Title IX discrimination complaint, not a lawsuit, against Harvard.

News from © The Associated Press, 2016