, Edwards said he indeed did have an affair with 44-year old Rielle Hunter, though he denied he was the father of Hunter's baby born earlier this year.
Edwards asserted, "Two years ago I made a very serious mistake, a mistake that I am responsible for and no one else. In 2006, I told Elizabeth about the mistake, asked her for her forgiveness, asked God for his forgiveness. And we have kept this within our family since that time."
Edwards, 55, said he told his entire family about the affair after it ended in 2006, and that his wife Elizabeth, who has incurable breast cancer, was "furious" but that their marriage would survive. The couple have three children, Cate, 25, Emma, 9, and Jack, 7.
A series of dramatic allegations revolving around the affair have been reported by the supermarket tabloid National Enquirer. The most serious of those allegations is that Hunter has been receiving hush money through the Edwards campaign in order to keep her quiet.
In the interview, Edwards denied knowing anything about any support being provided to Hunter or to Andrew Young, the former Edwards campaign aide who has said that he, not Edwards, is the child's father.
Friends of Reille Hunter told ABC that she and Edwards met in 2006 at a New York City bar, and that she received $114,000 from his political action committee to produce Web site documentaries for the Edwards campaign, despite her lack of experience.
Edwards said the affair started after she was employed and that Hunter accompanied him around the U.S. and to Africa. He also said his wife, Elizabeth, and other family members became aware of the relationship in 2006. Edwards stresses that his wife's cancer was in remission when he began the affair.
A friend remarked that Edwards never displayed any behavior that was inappropriate during his campaign. "Not at all. He didn't have a wandering eye," said the source.
In a statement issued separately, Edwards said, "I was and am ashamed of my conduct and choices, and I had hoped that it would never become public. With my family, I took responsibility for my actions in 2006 and today I take full responsibility publicly. But that misconduct took place for a short period in 2006. It ended then."
He also offered to undergo a paternity test to show that he was not the father of Hunter's child.
"You cannot beat me up more than I have already beaten up myself," the former U.S. senator from North Carolina and failed 2004 vice presidential candidate said.
"I have been stripped bare and will now work with everything I have to help my family and others who need my help," he said.
"In the course of several campaigns, I started to believe that I was special and became increasingly egocentric and narcissistic. If you want to beat me up -- feel free. You cannot beat me up more than I have already beaten up myself. I have been stripped bare and will now work with everything I have to help my family and others who need my help."
Edwards's wife, Elizabeth, 59, is battling breast cancer, first diagnosed in 2004. After initial treatment, Elizabeth Edwards announced last year that her cancer had returned and is incurable.
A friend of Elizabeth's, who has been in regular contact with her over recent weeks, told the People magazine: "She actually is okay. I'm pretty impressed by how she's handling it. And her health is stable."
Elizabeth Edwards says in her blog her husband John "made a terrible mistake" by having an affair, but coping with the revelation was "oddly made somewhat easier" by her battle with cancer.
"None of these (problems) has been easy," she writes. "But we have stood with one another through them all. Although John believes he should stand alone and take the consequences of his action now, when the door closes behind him, he has his family waiting for him."
She also said she had encouraged people to watch her husband's ABC news interview Friday.
"Admitting one's mistakes is a hard thing for anyone to do, and I am proud of the courage John showed by his honesty in the face of shame," she writes. "The toll on our family of news helicopters over our house and reporters in our driveway is yet unknown. But now the truth is out, and the repair work that began in 2006 will continue."
She concludes with a plea for privacy, saying, "I ask that the public, who expressed concern about the harm John's conduct has done to us, think also about the real harm that the present voyeurism does and give me and my family the privacy we need at this time."