June 22, 2012 -- Why did Rielle Hunter accept an invitation from John Edwards, a married man, to join him in his hotel room one fateful day in 2006?
"I went there because I believed I could help him," Hunter told "20/20's" Chris Cuomo in an exclusive interview.
Hunter reveals the details of her first meeting with the then-presidential candidate and the six-year affair that became the biggest political sex scandal of a generation in her bombshell tell-all, "What Really Happened: John Edwards, Our Daughter, and Me," to be published June 26. Hunter recently sat down with Chris Cuomo for her first interview since Edwards' acquittal on charges of accepting illegal campaign contributions.
In the book, Hunter writes that, as a budding spiritual advisor, she believed she could help him merge his public persona -- which she said appeared shallow and aloof -- with his deeper private persona, so that he could present himself more authentically.
The story of their love and scandal began with that hotel encounter.
"He rounded the street corner and it came out of my mouth: 'You're so hot,'" Hunter recalled.
Hunter is well aware that others might take her desire to "help" to mean something else.
"From the outside world looking in, (it's) like, 'Boy, did you sure help him,'" she told Cuomo.
Eventually, Hunter said, Edwards persuaded her to come sit with him on the hotel room bed.
"Something happened internally with me. I responded... I have not experienced it or felt what was happening before. Ever. An intensity like a rock concert. A lot of energy," she told Cuomo.
That energy was strong enough that the man who would soon be a candidate for president of the United States risked it all to be with her.
"We could not get enough of each other on the telephone," Hunter said. "If we were not together, we would be talking on the phone about four hours every night. We couldn't hang up."
Any doubts she had about sleeping with a married man were helped, she said, by his insistence that his storybook marriage with Elizabeth Edwards was just that -- a story.
"Their marriage was ruined before I got there. Years before I got there," Hunter said. She said Edwards told her he had had other mistresses -- that she was not the first.
To the public, meanwhile, Edwards presented an entirely different appearance.
"I was disgusted with myself for being in love with a man who was going on national TV with his wife -- and lying," Hunter said.
While Edwards was hot on the campaign trail, Hunter discovered that she was pregnant. Hunter said Edwards had a "gracious" reaction when she told him the news, saying he would support her and that he wouldn't tell her what to do.
"I think he thought the timing was terrible," she said, but Edwards was "kinder and more gentle than I thought he would be."
Hunter called the February 2008 birth of their daughter Quinn, now 4, "difficult and incredible."
"It's like the polar opposites of the pain and agony and oh my God, how difficult it is. But the blessing that comes out of that (is) amazing," she said.
But amid her amazement, Hunter was also devastated by Edwards' initial denial that he was Quinn's father. In an interview with ABC News' Bob Woodruff on Nightline in August 2008, he insisted that he was not Quinn's father. Still, Hunter said she understands why Edwards lied.
"What it meant, though, to me, is that he was temporarily insane. I mean, he had really gone off the deep end a bit there," she said, "but it was painful to witness."
Hunter said at one point she was asked to sign a confidentiality agreement requiring her to keep the identity of Quinn's father secret from everyone except Quinn. She refused.
"I didn't want my daughter growing up under a lie," she said.
The most controversial part of the book, however, may be what Hunter writes about Elizabeth Edwards. She was critical of how Elizabeth Edwards handled her own relationship with John Edwards and how she reacted to her husband's affair with Hunter. She said that Elizabeth Edwards used her cancer and her children as weapons in a war against a father trying to take care of his daughter.
But Hunter also maintained that she had "no desire to bash" Elizabeth Edwards.
"I have a great deal of compassion and empathy for her suffering. And I have no desire to bash Elizabeth. Elizabeth is the mother to my daughter's siblings. And she is, indirectly, now my family," she said.
Elizabeth Edwards died in 2010.
"What do you think the reaction is when the woman who's sleeping with the husband starts talking about the wife who is now dead from cancer?" Cuomo asked.
"There're a lot of people that'll go, 'Wow, I understand. I get it,'" Hunter said. "And then a lot of people will be outraged."
"I feel for both my daughter and for all the kids involved, the full truth needs to be in the public domain," she said. "Their father's not a demon and their mother's not a saint. And I'm not a home wrecker. We're real human beings. And there is a real dynamic that was going on, good and bad. And we all made mistakes."
Hunter said she has regrets about the affair, but the one thing she doesn't regret is having Quinn. She calls the little girl the love of her life.
In a written statement, family and close friends of Elizabeth Edwards responded to Hunter's criticism.
"All of us who knew and loved Elizabeth find it unfortunate that the character of this wonderful woman is being falsely criticized by someone who never knew her. Those who knew Elizabeth knew a kind, generous, brilliant woman who did not suffer fools. She was, for good reason, greatly admired by those who knew her speeches, her writings, and the wise counsel she gave to so many, so often. The memory of her wit, her heart, and her kindness will remain, for millions, untarnished, and especially so for her children, from whom she was taken too soon."