"What I saw yesterday is a man who realized he sinned," Tom Davis told "Good Morning America" today.
Sanford invoked Davis' name several times while admitting to the affair during Wednesday's press conference, emphasizing how he "let down the Tom Davises of the world."
Davis, a close family friend who lived in the family's basement for six months during Sanford's first race for governor in 2002, said that Sanford did let him down.
"I think I represent to him people that have believed in him, people that have believed in the powers of his ideas," Davis said.
Davis said he spoke with Sanford for about an hour and a half before the press conference. Up until that point, Davis said he had no idea that the governor's trip would blow up into such a wide-reaching scandal. His main concern, he said, was trying to explain Sanford's absence. (Sanford's staff had been told the governor was on a hiking trip in the Appalachian Mountains.)
Davis said that while he has not spoken to the governor's wife, Jenny Sanford, he believes his friend understands "the very real hurt he knows he caused people."
While some have begun calling for the governor's resignation, South Carolina's Republican leaders have stopped short of that. Instead, they are questioning whether Sanford used taxpayer money to finance his trips to Argentina to visit his mistress, known only as Maria.
During the press conference Wednesday, Sanford said that his eight-year friendship with Maria sparked a romance about a year ago and that he had seen her three times since the "whole sparking thing."
"He should not resign," Davis said, but noted that while Americans have a tremendous capacity for forgiveness, they also recognize hypocrisy.
ABC News' chief Washington correspondent George Stephanopoulos noted today on "Good Morning America" that Republican politicians have generally fared better than their Democratic counterparts after sex scandals.
While Sanford and Sen. John Ensign, R-Nev., who admitted an affair earlier this month, show no signs of resigning their posts, former New York Gov. Eliot Spitzer left his job after winning a landslide election when he got caught in a prostitution scandal. And former New Jersey Gov. Jim McGreevey also resigned after admitted to an affair with a male staff member.
He said Sanford's admission was unprecedented, in part, because of how candid he was about his infidelity.
"We've never seen anything like this & the raw emotion, the amount of information the governor gave out was simply incredible," Stephanopoulos said.
Mark Sanford's Trip to Buenos Aires
Sanford coyly sang the praises of his mistress's body and agonized over their "hopelessly impossible situation of love" in e-mails to the woman that emerged Wednesday, hours after the press conference.
The State, South Carolina's largest daily newspaper, which broke the news about Sanford's trip to Buenos Aires after speaking to him at the Atlanta airport upon his arrival this morning, obtained private e-mail exchanges between the governor and Maria.
When contacted by ABC News, Sanford's office did not dispute the authenticity of the e-mails.
In an e-mail dated July 10, 2008, Sanford writes that the two are in a "hopelessly impossible situation of love," and that he feels "a little vulnerable because this is ground I have never certainly never covered before."
"You have a particular grace and calm that I adore. You have a level of sophistication that so fitting with your beauty. I could digress and say that you have the ability to give magnificent gentle kisses, or that I love your tan lines or that I love the curve of your hips, the erotic beauty of you holding yourself (or two magnificent parts of yourself) in the faded glow of the night's light -- but hey, that would be going into sexual details," Sanford writes.
"In the meantime please sleep soundly knowing that despite the best efforts of my head my heart cries out for you, your voice, your body, the touch of your lips, the touch of your finger tips and an even deeper connection to your soul," the e-mail reads.
Maria, described as the mother of two sons, wrote in an e-mail June 9, 2008: "You are my love. ... Something hard to believe even for myself as it's also a kind of impossible love, not only because of distance but situation. Sometimes you don't choose things, they just happen. ... I can't redirect my feelings and I am very happy with mine towards you." The affair, Sanford said at his press conference today, began "casually," but over the "last year developed into something much more."
"We developed a remarkable friendship over those eight years and then ... about a year ago it sparked into something more than that," Sanford said. "I have seen her three times since then, during that whole sparking thing. ... And it was discovered ... five months ago. And at that point, we went into serious overdrive in trying to say, 'Where do you go from here.'"
Jenny Sanford Asked Governor to Move Out
Sanford also resigned from his position as chairman of the Republican Governors Association, saying he would need time to seek forgiveness from friends and family and to focus on what he called a "very long process." Sanford said in the press conference that his wife of nearly 20 years was aware of his affair before he left for Argentina, and that the family had been trying to work through the situation for "about the last five months."
In a written statement, his wife, Jenny Sanford, said, " I deeply regret the recent actions of my husband Mark, and their potential damage to our children."
She said she asked her husband to leave two weeks ago and to not contact her or their four sons, which explains why the family was unaware of the governor's whereabouts during his unexpected disappearance.
"When I found out about my husband's infidelity I worked immediately to first seek reconciliation through forgiveness, and then to work diligently to repair our marriage," she said in a release. "We reached a point where I felt it was important to look my sons in the eyes and maintain my dignity, self-respect, and my basic sense of right and wrong."
But South Carolina's first lady hinted that she was willing to forgive her husband and that "this trial separation was agreed to with the goal of ultimately strengthening our marriage."
Invoking the Bible, she said: "I remain willing to forgive Mark completely for his indiscretions and to welcome him back, in time, if he continues to work toward reconciliation with a true spirit of humility and repentance."
The couple started their careers on Wall Street, where Jenny Sanford was a vice president in mergers and acquisitions at the investment bank Lazard Freres, The Associated Press reports. The couple met in the Hamptons, Long Island, married and headed to South Carolina.
When the governor was asked today whether he was separated from his wife, he responded: "I don't know how you want to define that. I'm here, she's there. I guess in a formal sense we're not."
An emotional Sanford, who spoke about "God's law" several times in his press conference, said he needed a break from his job after what he called an "exhausting" battle against President Obama's stimulus bill.
Sanford did not answer a question from a reporter asking him whether he would resign as governor, but he did say in a written statement afterward that "I'm going to devote my energy to building back the trust the people of this state have placed in me."
"What I did was wrong, period, end of story," Sanford said at the press conference. "I'm committed to trying to get my heart right. This was selfishness on my part."
This is the second such scandal to rock the GOP this month. Earlier this month, Sen. John Ensign, R-Nev., admitted to an affair with a campaign staffer and resigned as leader of the Republican Policy Committee.
Almost immediately after Sanford's resignation as chairman of RGA, the organization announced that Mississippi Gov. Haley Barbour will take over as chairman.
"My job allows me to share the joys of getting to know great leaders around the country and experiencing great pride when they succeed, but the other side of that is experiencing deep disappointment when they fall short," said RGA executive director Nick Ayers. "Today is undeniably a disappointing day."
South Carolina residents expressed mixed views.
"Here you are cheating. That doesn't stand right with me at all as a woman," Zippora Gregory told ABC News.
"It's happened in politics before and I'm sure it's never going to end," said Camillo Miller.
Sanford 'Taken Aback by All the Interest'
Sanford told the State newspaper t that he didn't know why his staff said he was on the Appalachian Trail, but that "in fairness to his staff," he had told them he might do that.
"I would also apologize to my staff. I let them down by creating a fiction about where I was going," Sanford said in the press conference, and added that he did not ask any of his employees to cover up the affair.
A U.S. Embassy official in Argentina told ABC News the embassy had "absolutely no idea" that Sanford was in the country, adding that this comes "from out of left field. It would be extremely odd that a U.S. governor would not check in with the embassy."
But a Department of State spokesperson said if Sanford decided to travel as a private citizen, the department would not have to be informed.
Earlier this week, Sanford's family and staff said they were not concerned. His office said in a statement that it was not uncommon for the governor to "go out of pocket for a few days at a time to clear his head."
Jenny Sanford told The Associated Press Monday that the governor was "writing something and wanted some space to get away from the kids."
But what ignited national curiosity was that Sanford's security agents were unaware of his whereabouts and Lt. Gov. Andre Bauer -- who would be in charge in the governor's absence - said he didn't even know Sanford was going away.
This morning Sanford flew back to Atlanta rather than to Columbia, S.C., to avoid a media stampede.
Sanford's communication director said Tuesday, "It would be fair to say the governor was somewhat taken aback by all the interest this trip has gotten."
Sanford Leading Opponent of Obama's Stimulus Plan
Sanford recently emerged as an outspoken opponent to President Obama's $787 billion stimulus plan, becoming the only governor to reject the federal stimulus money.
Instead of using the $700 million in stimulus money to fund projects, Sanford argued that the money instead be used to pay down South Carolina's deficit, an argument rejected by the federal government. He also lost in court when South Carolina's Supreme Court ruled that the governor had to accept the money.
In an ABC News interview earlier this month, Sanford said the Supreme Court decision did not come as a surprise, but that he still disagreed with the federal government's assessment that the stimulus will help boost his state's economy.
"The problem was if you spent all the stimulus money in our state, what it meant was that you dig for yourself about a billion dollar financial hole 24 months from now, and then the question was, and then what? I think it's financially reckless to embark on a journey to put you about a billion dollars in the hole in 24 months," he said. "The other part of the objection was the reform and restructuring that won't take place. What this amount of federal money allows you to do is to pay for all the changes that would've been made under more austere financial conditions."
"What this medicine out of Washington does is in fact weaken our state in the long run," he said.
Additionally, the South Carolina Legislature last week overturned all 10 of Sanford's vetoes on the stimulus.
While he may like to keep under the radar, there were some questions -- before the news of the affair -- that Sanford may consider a run for the presidency in 2012. The governor told ABC News that right now, "it's not my focus, it's not my aim, it's not my intent," but added "you never say never."
Those ambitions, some say, may be dashed for now.