Link In a stunning confession, South Carolina Gov. Mark Sanford admitted Wednesday to being "unfaithful" to his wife during a press conference meant to clear up his mysterious week-long absence. "I've let down a lot of people. That's the bottom line," he said. "I've been unfaithful to my wife." Sanford, who just returned from Argentina, said he developed a "relationship with what started out as a dear, dear friend" from that country. "It began very innocently as I suspect they usually do ... Over this year (it) developed into something much more than that," he said. The governor "apologized" profusely to his family, his staff and the people of South Carolina. He said he's let down his four sons in a "profound way," though he said his wife Jenny had known about the affair for five months and they were trying to work through it. He said he is resigning as chairman of the Republican Governors Association. The first-hand account Wednesday was meant to settle mounting questions over the governor's week-long disappearance. His staff first claimed the governor was hiking on the Appalachian Trail a few hours away from the state capital. But confusion intensified Wednesday morning after The State newspaper reported that Sanford had just returned from Argentina. It became clear early in his press conference that Sanford would reveal something much more personal surrounding his trip, as he repeatedly made reference to his family and apologized for his behavior.