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.
Watch Chris Cuomo's interview with Rielle Hunter tonight on "20/20" at 10 p.m. ET.
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.
PHOTOS: Rielle Hunter, John Edwards and Their Daughter
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.
Eyewitness NewsSTAMFORD, Conn. (WABC) -- An advertising executive's three daughters and parents were killed in a fire at her home along the Connecticut shoreline Sunday.