South Carolina Gov. Mark Sanford admitted Wednesday that he's been having an affair with a woman from Argentina-- the country he spent the last five days in during an unexplained absence.

Speaking at a press conference, Sanford apologized to his wife and said he will step down as head of the Republican Governors' Association.  Several GOP leaders had eyed him as a top contendor for the 2012 presidential election.

"I've let down a lot of people. That's the bottom line," he said

Sanford added that his wife, Jenny, has known about the affair for five months.  She asked her husband to leave and stop talking to her two weeks ago.  The pair have four sons together, none of which attended the press conference.

"This trial separation was agreed to with the goal of ultimately strengthening our marriage," she said.

Sanford met the other woman about eight years ago but said the two didn't become intimate until a little over a year ago.

Click play for CBN News analysis of Sanford's confession and comments from Gerson Moreno-Riano of the Regent University School of Government.

Sanford, returned to work Wednesday after an unexplained five-day absence, which he said he took because he "needed a break."

Previous reports said that he was hiking the Appalachian Trail, but Sanford revealed that he in fact spent the last five days "crying in Argentina."

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

In an emotional apology, Sanford assured his family the affair has ended and that he would like to repair his marriage.  In a statement, Jenny Sanford did says her husband has earned that chance.

After the revelation, at least one lawmaker called for the South Carolina governor's resignation.

As Congressman, Sanford voted in favor of most of the measures to impeach former President Bill Clinton, citing a need for "moral legitimacy."

Sources: CBN News, The Associated Press