COLUMBIA — In a spectacular personal and political collapse, Gov. Mark Sanford admitted Wednesday that he had an extramarital affair with a woman who lives in Argentina and that he lied to his staff about a secret trip he took to be with her last week.

After six days of speculation about his whereabouts, Sanford walked out of his office in the Statehouse and held an emotional news conference in the lobby. "I let down a lot of people," he said, his eyes brimming with tears. "That's the bottom line."

Sanford explained that the affair with the woman, whom he did not name, started about a year ago, and that his wife, Jenny, knew about the relationship before he traveled to Argentina.

The first lady issued a statement two hours later saying that she had asked him to leave the house two weeks ago, hoping that "this trial separation" would strengthen their marriage.

"I kept this separation quiet out of respect of his public office and reputation, and in hopes of keeping our children from just this type of public exposure," she said. "Because of this separation, I did not know where he was in the past week."

It was a stunning moment for a governor whose political star has been on the rise to the point that he has been mentioned as a potential presidential candidate in 2012. Sanford built his political credentials by holding fast to principles, both moral and economic. But his public confession was remarkable on many levels.

On a national level, Sanford's story of infidelity was more bad news for Republicans struggling in the wake

Republicans struggling in the wake of last year's election loss. During the news conference Sanford resigned as chairman of the Republican Governors Association, but indicated he wouldn't resign as governor. Political analysts said nevertheless that Sanford's national political prospects now are dim.

On a personal level, his admission touched on his long-standing frustrations with being in the public eye, while his wife's statement reflected the pain of a troubled marriage and the consequences this can have on others.

It began as a friendship

A few minutes after 2 p.m., Sanford strode from his office in the Statehouse to face a phalanx of about 80 reporters and television people. He was wearing a blue suit and looked tan but tired. The governor fumbled with his hands for a moment amid a cluster of microphones on a wooden lectern as photographers snapped photos.

He began by mentioning an encounter earlier in the morning with a reporter from The State newspaper, who met him at the Atlanta airport and asked about his reported trip on the Appalachian Trail.

For two days, Sanford's aides had insisted that the governor merely took time off to go hiking in the mountains. But the reporter's presence at the airport immediately blew his cover, and he admitted then that he had been in South America.

Sanford said during the news conference that he knew he would have to come clean. "I'm a bottom line kind of guy. It's going to hurt. I'm going to let the chips fall where they may," he said.

He said he met his mistress eight years ago, though he didn't say where. "I met this person and struck up a conversation," Sanford said. "There's a certain irony to this. She was separated, and we ended up with this incredibly serious conversation and about why she should get back with her husband for her boys."

They decided to stay in contact via e-mail. "It started on a very casual basis — run things by each other," he said. He felt as if he had found a confidant. "When you live in the zone of politics, you can't ever let your guard down. You can't ever say, 'What do you think, what do you think?' There was this zone of protectiveness. She lived thousands of miles away, and I was up here, and you could throw an idea out and vise versa.

"We developed a remarkable friendship over those eight years. About a year ago, it sparked into something more than that."

Progressed to intimacy

For instance, just after midnight last July 10, Sanford sent an e-mail to the woman, identified as "Maria" in e-mails obtained by The State newspaper.

"Two, mutual feelings. ... You have a particular grace and calm that I adore. You have a level of sophistication that's so fitting with your beauty. I could digress and say that you have the ability to give magnificent gentle kisses, or that I love your tan lines or that I love the curve of your hips, the erotic beauty of you holding yourself (or two magnificent parts of yourself) in the faded glow of the night's light — but, hey, that would be going into sexual details. . . ."

Sanford went on to describe their love as "impossible," and "how in the world this lightening strike snuck up on us I am still not quite sure. As I have said to you before I certainly had a special feeling about you from the first time we met, but these feelings were contained and I genuinely enjoyed our special friendship and the comparing of all too many personal notes."

His wife finds out

Sanford said his wife learned of his infidelity about five months ago.

Jenny Sanford said that when she found out about the affair, "I worked immediately to first seek reconciliation through forgiveness, and then to work diligently to repair our marriage. We reached a point where I felt it was important to look my sons in the eyes and maintain my dignity, self-respect, and my basic sense of right and wrong. I therefore asked my husband to leave two weeks ago."

Sanford seemed to suggest in the news conference that he was actually considering going on a hike, but that he ended up in Argentina. "I spent the last five days crying in Argentina only to come back here and cry," he said.

When a reporter asked whether he had broken off the relationship with the woman, he said he had been trying to get his "heart right," and that they were in different places in their lives.

Sanford spent a great deal of time talking about the consequences of his actions. He said he was particularly ashamed about the revelation's effect on people with strong religious beliefs.

On a more personal level, he acknowledged harming his family and friends. "I hurt you all," he said. "I hurt my wife. I hurt the boys. I hurt friends like (state senator and former chief of staff) Tom Davis. I hurt a lot of people. And all I can say is, 'I apologize.' "

Choking back tears, he recalled a "surreal" conversation a couple of weeks ago with his wife's father about the affair. "He was incredibly gentlemanly as you cannot imagine," Sanford said. "Here was the pain I was struggling with in regards to where my heart was and where I was in my life, and I let him down and a lot of people, and that's the bottom line."

Sanford also confessed that he had misled his staff. "I would apologize to my staff as much as I did talk about going on the Appalachian Trail. That isn't where I ended up."

More questions

While Sanford's startling confession answered questions about his whereabouts last week, it raised new questions about his marriage and political future.

Unlike so many other politicians' wives who have seen their husbands' infidelities exposed and stood next to them in news conferences, Jenny was home with her parents and children. Her only comments came in a lengthy statement.

"I would like to start by saying I love my husband and I believe I have put forth every effort possible to be the best wife I can be during our almost twenty years of marriage," she said.

She said she was proud of his accomplishments, but that "the greatest legacy I will leave in this world is the character of the children I, or we, leave behind. It is for that reason that I deeply regret the recent actions of my husband, Mark, and their potential damage to our children."

She concluded by saying that she believed in the power of marriage, and that "Mark has earned a chance to resurrect our marriage. Psalm 127 states that sons are a gift from the Lord, and children a reward from Him. I will continue to pour my energy into raising our sons to be honorable young men. I remain willing to forgive Mark completely for his indiscretions and to welcome him back, in time, if he continues to work toward reconciliation with a true spirit of humility and repentance."

Sanford said he has many hard decisions to make. "I am committed to that process of walking through with Jenny and the boys, the Tom Davises of the world and the people of South Carolina," he said. "I go back to that simple word of asking for forgiveness."