ATLANTA, (Reuters) – South Carolina Governor Mark  Sanford tearfully admitted yesterday he had been unfaithful  to his wife, likely ending any chance he might be a Republican  contender for the U.S. presidency in 2012.

Sanford resigned as chairman of the Republican Governors’  Association and was replaced by Mississippi Governor Haley  Barbour, another possible 2012 candidate.

“Any aspirations for 2012, if he had any, are certainly out  of the question,” said Robert Oldendick, a political scientist  at the University of South Carolina.

Sanford’s confession at a tumultuous news conference ended  days of speculation over his whereabouts. After he disappeared  last week, his staff first said he was hiking on the  Appalachian Trail. It later emerged he had travelled to  Argentina to be with his lover, leaving his family over  Father’s Day weekend.

“I spent the last five days of my life crying in  Argentina,” he said.

Shedding tears, Sanford apologized to his wife Jenny, his  family, friends and staff when he made the shock announcement  after returning yesterday from Buenos Aires.

Sanford’s wife Jenny said she and her husband had been  undergoing a trial separation and she regretted his actions and  the damage it had done to their children.

But she added in a statement: “I remain willing to forgive  Mark completely his indiscretions and to welcome him back.”

Sanford explained how he had “developed a relationship”  with a “dear friend” from Argentina. “It began very innocently  … in just a casual e-mail back and forth,” he said.

“But here recently over this last year it 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 … I hurt a lot of different folks.”

With his tearful admission and grovelling apologies, Sanford  became the latest member of a fast-growing club of U.S.  politicians who have confessed their sexual indiscretions  before a public audience.

Sanford was one of several Republican governors seen as  possible 2012 presidential candidates. Others include Alaska  Governor Sarah Palin, Minnesota’s Tim Pawlenty, and Louisiana  Governor Bobby Jindal.

As chairman of the governors’ association Sanford has been  one of the party’s most visible spokesmen when its fortunes are  at a low ebb.

Last week, Senator John Ensign, another potential  Republican presidential contender in 2012, announced he had an  affair and resigned from the Senate leadership.