(CNN) -- Former U.S. senator and Democratic presidential hopeful John Edwards admitted Friday to an extramarital affair. He denied being the father of the woman's child, as had been alleged in tabloid reports.

Former Sen. John Edwards told ABC News that he had an affair with Rielle Hunter, seen above.

In an interview on ABC News "Nightline," Edwards acknowledged the affair with 42-year-old Rielle Hunter, which began after she was hired to make documentary videos for his campaign, ABC said.

"I am responsible for it. I alone am responsible for it," Edwards said on ABC News "Nightline."

Edwards told the network that his rise from "a small town boy in North Carolina" who "came from nothing" to a successful lawyer, U.S. senator and national public figure "fed a self-focus, an egotism, a narcissism that leads you to believe that you can do whatever you want."

Edwards, in the ABC interview, acknowledged meeting with Hunter at the Beverly Hills hotel at the request of a friend of hers.

"I was there from a very simple reason, because I was trying to keep this mistake that I had made from becoming public," Edwards said.

In a written statement Friday, Edwards said, "In 2006, I made a serious error in judgment and conducted myself in a way that was disloyal to my family and to my core beliefs. I recognized my mistake and I told my wife that I had a liaison with another woman, and I asked for her forgiveness."

"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." Read the full statement

Edwards said a blurry photograph published by the National Enquirer that purportedly showed him holding Hunter's child inside the hotel room could not be authentic, since the baby was not there at their meeting.

"I don't know if the picture has been altered, manufactured, if it's a picture of me taken some other time, holding another baby. I have no idea," he said. "I was not at this meeting holding a child for my photograph to be taken, I can tell you that."

Edwards said he has not taken a paternity test but that the timing of the affair rules out the possibility that he could be the father of Hunter's 5-month-old child. Edwards said Friday night he is "truly hopeful" that a paternity test will be done to squelch the rumors.

Andrew Young, a former Edwards campaign aide who is married, has publicly said he fathered the child. The Washington Post reported Friday that Hunter acknowledged Young as the father.

When the National Enquirer first reported the affair in October, Edwards flatly denied it, calling the claims "false" and "ridiculous." Watch an interview with the National Enquirer's editor »

Contacted through a former aide by CNN on Thursday, Edwards had refused to comment on the reports. He also dodged reporters at a recent event in Washington.

In a July 24 appearance in New Orleans, Louisiana, he would not answer a reporter's question about whether he had provided financial support to Hunter or Young. Watch Edwards says "I sin every single day" »

"I have no idea what you're asking about," Edwards said. "I have responded to, consistently, to these tabloid allegations by saying I don't respond to these lies."

Edwards, 55, of North Carolina, told ABC that his wife, Elizabeth, and other family members have known about the affair since 2006.

Elizabeth Edwards, in a posting on the Daily Kos Web site, said:

"The fact that it is a mistake that many others have made before him did not make it any easier for me to hear when he told me what he had done. But he did tell me. And we began a long and painful process in 2006, a process oddly made somewhat easier with my [cancer] diagnosis in March of 2007. This was our private matter, and I frankly wanted it to be private because as painful as it was I did not want to have to play it out on a public stage as well."

Edwards, the vice presidential candidate during Sen. John Kerry's 2004 presidential bid, told ABC that he never expected to be chosen as Sen. Barack Obama's running mate, but that his public career has not ended. He said he would not worry about any possible positions in an Obama administration.

"I don't know what's possible and what's gone," he said.

Don Fowler, a former Democratic Party chairman, said this week that Edwards might be forfeiting a major role at the party's upcoming convention in Denver -- or in a future Democratic administration -- unless he cleared the air.

"I think the longer these allegations go unanswered and unresponded to, the more difficult it is for the people producing the convention to give him a prominent spot," Fowler said. iReport: What's your reaction to Edwards' affair?

Fowler, of South Carolina, served as Democratic chairman from 1995 to 1997 and will be a party superdelegate at the Denver convention in late August. He said he had no input into whether Edwards addresses the convention, "but I would expect that he would not speak or have any role at the convention unless this is cleared up." Watch more on the Edwards controversy »

Obama, in Hawaii for a weeklong vacation, told reporters he understands that Edwards does not plan to attend the convention.

"This is a difficult and painful time for them, and I think they need to work through that process of healing," he said. "My sense is that that's going to be their top priority.

"John Edwards was a great champion of working people during the first of this campaign. Many of his themes are ones that Democrats as a whole share; those will be amplified at the convention," Obama added.

Presumptive Republican nominee Sen. John McCain declined to comment on a similar question.

Speaking in support of Obama in Las Vegas, Nevada, on Friday, Edwards' former rival, Sen. Hillary Clinton, responded briefly to a reporter's question about what, if any, impact the revelation of the affair would have on Democrats.

"My thoughts and prayers are with the Edwards family today," she said. "That's all I have to say."

The Enquirer's claims about the affair were revived July 22 when the tabloid reported it had confronted Edwards at a Beverly Hills, California, hotel after receiving a tip he was meeting Hunter and her child there.

On Friday, he said he was ashamed of the affair and hoped it would never become public. He said he used the fact that the Enquirer story "contained many falsities" to deny it.

"But being 99 percent honest is no longer enough," he said in the statement.

Edwards told ABC that his wife's widely reported cancer was in remission when the affair began.

"She was mad; she was angry," Edwards said, describing when he admitted the affair to his wife. "I think furious would be a good way to describe it." Watch Edwards describe his wife's reaction »

According to federal election records, the Edwards campaign paid Hunter's production company roughly $114,000 in 2006 and 2007 for "Website/Internet services."

The former North Carolina senator announced in January that he was dropping out of the 2008 Democratic presidential race.

"It is time for me to step aside so that history can blaze its path," he said in New Orleans.

With his wife and children at his side, Edwards said he couldn't predict "who will take the final steps to 1600 Pennsylvania Avenue," but he said it would be a Democrat.

Edwards endorsed Sen. Barack Obama on May 14 during a rally in Grand Rapids, Michigan.

He trailed Clinton and Obama in the early contests. He came in third in key races in New Hampshire and South Carolina.

Edwards had campaigned on the message that he was standing up for the little guy, the people who are not traditionally given a voice in Washington, and that he would do more to fight special interests.

After dropping out of the race, Edwards asked Clinton and Obama to make poverty a central issue in the general election and a future Democratic administration, something both agreed to do.

Edwards is a South Carolina native with an undergraduate degree from North Carolina State University and law degree from the University of North Carolina.

Before entering politics, winning a Senate seat from North Carolina in 1998, Edwards was a lawyer representing families "being victimized by powerful interests" and gaining "a national reputation as a forceful and tireless champion for regular, hard-working people," according to his campaign Web site.

CNN's Ed Hornick, Scott Bronstein, Drew Griffin, Matt Smith and Paul Vercammen contributed to this report.

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