For more than 10 years, it was something Mindy McGillivray said she shared only with a close circle of family and friends.

That changed Sunday night. Donald Trump was asked during the presidential debate about when he bragged that he kissed women without their consent and grabbed their genitals – remarks captured on audio that surfaced last week.

Trump apologized for the remarks and dismissed them as "locker room talk." But the debate moderator, CNN’s Anderson Cooper, asked Trump to clarify: "Have you ever done those things?"

"No, I have not,’’ Trump replied.

Watching at home in Palm Springs, Fla., McGillivray said she rose from her couch and yelled at the TV screen: "‘You liar!’’’

McGillivray, 36, said she was groped by Trump at Mar-a-Lago 13 years ago. She said she never reported it to authorities.

But her companion that day, photographer Ken Davidoff, vividly remembers when McGillivray pulled him aside moments after the alleged incident and told him, ‘’Donald just grabbed my ass!’’

The New York Times reported Wednesday that two other women came forward to say Trump groped them — one who sat next to him on a flight 30 years ago and another who encountered him outside an elevator at Trump Tower.

>>See who painted the Mar-a-Lago portrait of Donald Trump

"There is no truth to this whatsoever," Hope Hicks, Trump’s press secretary, said about McGillivray’s allegation when reached by The Post Wednesday night. "This allegation lacks any merit or veracity."

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According to Davidoff, it was Jan. 24, 2003, when he and his father, the late Palm Beach society photographer Bob Davidoff, took photos at Mar-a-Lago during a concert by Ray Charles. Bob Davidoff for years was the Kennedys’ favored photographer in Palm Beach.

Ken Davidoff said he brought his friend McGillivray to help him during the concert. Her job was to keep numbered name plates of everyone the Davidoffs photographed.

The Davidoffs were the official photographers of Mar-a-Lago, a deal they got only after Trump demanded he get 20 percent of their proceeds, Ken Davidoff said.

McGillivray, who was 23 at the time, said it was one of five or six times she helped Davidoff on photo shoots at Mar-a-Lago.

"Ken says, ‘We’re going to get backstage. Ray Charles is going to be there.’ He was one of my idols,’’ she recalled. "Ken wanted to get a picture of me and Ray, but that didn’t happen because he had all these bodyguards.’’

After the show, Davidoff and McGillivray were standing in a pavilion behind the main house in the middle of a group of people. To their left was Regis Philbin and his wife, Joy, according to Davidoff. To McGillivray’s immediate right was Trump and his now-wife, Melania.

"Ray already performed. He’s ready to leave. He’s saying his goodbyes to everyone,’’ McGillivray recalled.

"All of a sudden I felt a grab, a little nudge. I think it’s Ken’s camera bag, that was my first instinct. I turn around and there’s Donald. He sort of looked away quickly. I quickly turned back, facing Ray Charles, and I’m stunned.’’

McGillivray said she remembers saying to herself, ‘’‘OK, am I going to say something now and make a scene or be quiet?’ I chose to stay quiet.’’

Davidoff said he did not witness the alleged groping but he said he has never had any reason to doubt McGillivray.

Asked about the possibility that what she felt was Trump or someone accidentally bumping into her, McGillivray said no. "This was a pretty good nudge. More of a grab,’’ she said. "It was pretty close to the center of my butt. I was startled. I jumped.’’

She said she had had another encounter with Trump about two years earlier at Mar-a-Lago, when she helped Davidoff photograph a New Year’s Eve party in 2001.

She was walking out of a restroom "and Donald caught me right before I headed downstairs. He goes, ‘It’s a cool evening, isn’t it?’’’ she said, mocking his voice. "He had this debonair tone. He was totally flirting,’’ she said.

"And then here comes Melania to save the day. She sees me. She had this shawl on because it was cold on New Year’s. And she whips the shawl behind her neck and storms off into the bathroom. I made a quick pivot and went straight downstairs and he went after her.’’

After the alleged groping incident, McGillivray never encountered Trump again. She said the incident is something she and her family and the Davidoffs would bring up periodically over the years, sometimes joking about it.

When Trump entered the presidential race, she said she started telling the story to more friends. One day last week, Davidoff came across a photo his father took that night in 2003 of Trump and Charles.

"He sent it to me and was like, ‘Remember that night?’ ‘Oh, yeah. I remember that night,’’’ McGillivray said.

When Trump told Cooper during the debate Sunday that he never groped a woman, McGillivray said she started to consider sharing her story. With Davidoff’s help, she reached out separately to The Palm Beach Post and to a Hillary Clinton campaign office on Lake Worth Road.

She knows her past may be scrutinized. She told The Post she has numerous traffic infractions over the years and two felony arrests. She was arrested when she was 17 for breaking into a school and got probation. And in 2012, she was arrested on DUI and child neglect charges because a child was in the car. She was adjudicated guilty of a misdemeanor.

She is registered to vote as having no party affiliation. She said she would have loved to see Bernie Sanders win the Democratic nomination but she will vote for Clinton.

It’s important "to set a good example for my daughter,’’ she told The Post. "It’s a respect issue for all women. If something like this happens to you, you should speak up.’’

Staff researcher Melanie Mena contributed to this story.