Mark Sanford, the Republican governor or South Carolina, finally ended the mystery over a bizarre week-long disappearance by confessing on live television yesterday that he had been having an affair with a woman in Argentina.

At an emotional press conference in which he spent several minutes reminiscing about childhood holidays and rambled about “God’s laws”, he eventually said: “I’m a bottom line kind of guy I’m just gonna lay it out. It’s gonna hurt and I’m going to let the chips fall where they may.”

Mr Sanford who - until this week - had often been mentioned as a likely contender for his party’s 2012 presidential nomination, fought back tears as he added: “I have been unfaithful to my wife. I developed a relationship with what started out as a dear, dear friend from Argentina.

“It began very innocently, as I suspect these things do, in just a casual e-mail back and forth. But here, recently, over this last year, developed into something much more than that. And as a consequence, I hurt her. I hurt you all, I hurt my wife. I hurt my boys. I hurt friends like Tom Davis. I hurt a lot of different folks.”

Surrounded by dozens of reporters and grinning spectators at the South Carolina statehouse, he pleaded with the press for a “zone of privacy” for his family while they tried to work out their future. “I would ask for y’all’s indulgence, not for me, but for Jenny and the boys,” the Governor said.

His wife had been told of the affair five months ago. Asked if he had separated from her, Mr Sanford responded: “I don’t know how you want to define that. She’s there, I’m here.” He added: “What I did was wrong, period. I spent the last five days crying in Argentina.” Three of his sons are teenagers and a fourth is 10.

Mr Sanford announced that he was resigning his position as chairman of the Republican Governors Association. His final term as leading the socially conservative state of South Carolina ends in 2011 and his political future must now be clouded in deep doubt.

The Governor said that he had met his unnamed lover eight years ago but their relationship had become sexual only in the past 12 months or so. He described how “God’s laws” were designed to “protect us from ourselves” before adding: “This was selfishness on my part.”

A blaze of rumours and speculation about him had sparked into life on Friday last week when it first emerged the Governor had slipped his security detail and headed off to an unknown destination out of contact even to members of his family.

On Tuesday, after fully four days — including the Father’s Day weekend — in which the chief executive of a state with 4,479,000 people and an annual budget of $21 billion was missing, aides sought to quieten a growing media frenzy by announcing that he had telephoned them to say he was hiking somewhere along the 2,175-mile Appalachia Trail which runs from Maine to Georgia.

Yesterday morning, however, he was confronted by a reporter at the Hartsfield-Jackson International Airport on his return to the state and acknowleged that he had been in Buenos Aires.

Mr Sanford claimed that he had decided at the last minute to go somewhere “exotic” but declined to give further details of the trip other than to say that he had been alone and had driven along the coastline.

Although he has previously raised eyebrows for bringing defecating pigs into the statehouse to make his case against so-called pork barrel spending, Mr Sanford was highly regarded as a maverick, even iconoclast, in conservative circles and had earned a national profile for trying to refuse $700 million of federal funds allocated to his state from President Obama’s stimulus programme.

He is the second potential Republican presidential runner to announce an affair in recent days. John Ensign, a Nevada Senator, last week admitted to a relationship with a married former campaign aide which was “absolutely the worst thing I have ever done in my life”. It later emerged that he had felt compelled to make the disclosure because the woman’s husband had tried to blackmail him. Mr Ensign, a member of his church’s “Promise Keepers” group dedicated to marital fidelity, has resigned from his party's national leadership.

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