"I've let down a lot of people, that's the bottom line," the 49-year-old governor said at a news conference where he choked up as he ruminated with remarkable frankness on God's law, moral absolutes and following one's heart. His family did not attend.

The woman, who lives in Argentina, has been a "dear, dear friend" for about eight years but, Sanford said, the relationship didn't become romantic until a little over a year ago. He's seen her three times since then, and his wife found out about it five months ago.

He told reporters he spent "the last five days of my life crying in Argentina" and the affair is now over. Sanford, a rumored 2012 presidential candidate, refused to say whether he'll leave office.

"What I did was wrong. Period," he said.