In January 1998, President Bill Clinton stood next to his wife, Hillary, as he delivered a clear message to America: “I did not have sexual relations with that woman, Miss Lewinsky.”

Of course, the 49-year-old was addressing the allegations that he had entered into an affair with Monica Lewinsky, a 22-year-old intern at the White House.

However, in court, Lewinsky presented a semen-stained blue dress, which provided DNA evidence of her affair with the President of the United States.

In August 1998, President Clinton finally confessed to his lie: “Indeed, I did have a relationship with Miss Lewinsky that was not appropriate”.

"I misled people, including even my wife," he said in the televised press conference.

It was confirmed that Clinton and Lewinsky began a sexual relationship in November 1995, which continued until March 1997.

By the end of 1998, Clinton would become the second President to have an impeachment investigation launched against him. He was acquitted of impeachment charges the next year, but there no longer was any doubt over Clinton's affair.

Since then, Hillary Clinton has rarely commented publicly on her husband's infidelity, or her decision to stay married to him.

But in an interview with Good Morning America, the 2016 presidential candidate made an unexpected admission when asked what the gutsiest decision she's ever made is.

"I think the gutsiest thing I’ve ever done — well, personally — was make the decision to stay in my marriage," she replied.

"Publicly, politically — run for president and keep going," she added. "Just get up every day and keep going."

Hillary Clinton on her marriage to Bill Clinton. Post continues after video. 

Her admission was surprising to even her daughter Chelsea Clinton, who was with her mother in the interview, as the two promoted their new book, The Book of Gutsy Women: Favorite Stories of Courage and Resilience.

Chelsea was speechless. "Oh, goodness. I think I’m so overwhelmed by my mother’s answer that I’m a bit out of words.

"I’m so proud to be her daughter."

Although such an admission is indeed rare, it is not the first time the former First Lady has indirectly commented on her husband's affair.

In 2017, Clinton opened up about the impact of the affair on her emotionally, in her memoir What Happened.

"There were times that I was deeply unsure about whether our marriage could or should survive," she said, omitting any specific reference to the scandal.

"But on those days I asked myself the question that mattered most to me: Do I still love him? And can I still be in this marriage without becoming unrecognisable to myself-twisted by anger, resentment, or remoteness.

"The answers were always yes. So I kept going."

Sign up for the "Mamamia Daily" newsletter. Your morning hit of the top news stories, to be consumed with a coffee in hand.