A top state Republican called for his resignation, and South Carolina's top senator questioned whether Sanford broke the law when he disappeared for several days on a trip to South America and didn't transfer power to the lieutenant governor.
Glenn McCall, one of two national representatives to the Republican National Committee and a county party chairman, said Thursday that party members want Sanford out. He said Sanford should practice the philosophy he's preached of holding GOP leaders accountable.
"He talked about how our leaders have stepped away from our core values and said one thing on the campaign trail or out in the public and did something different in the background," McCall said. "I think our party can recover from this if we hold him accountable and the governor does the right thing and resigns for the sake of the party."
GOP Sen. Glenn McConnell, the state's top senator, said Sanford needed to answer questions about whether taxpayer money was used during the affair, but stopped short of calling for an investigation. Sanford's spokesman has said no state resources were used.
Sanford's wife, Jenny, said in a statement Wednesday that she had kicked him out two weeks ago and asked him not to speak to her while she came to terms with his infidelity, but spokesman Joel Sawyer said they were together at the family's beach house Thursday. The Sanfords have four sons.
"The governor is in Sullivans Island with his family," Sawyer said. "He's also going to be spending some time today and spent some time last night as well touching base with other elected officials."
Sanford was a three-term U.S. House veteran who once cited "moral legitimacy" when he was a congressman voting for President Bill Clinton's impeachment, but he has taken a swan dive from the moral high ground.
By admitting to an extramarital affair, the Republican governor makes the already-difficult end of his term-limited administration nearly untenable.
Sanford was raising his national political profile with his outspoken fight against using federal cash for anything but paying down debt. As chairman of the Republican Governors Association, he was raising money for candidates and deflecting talk he was planning to run for president in 2012.
The speed of his collapse was shocking. Even his former chief of staff and friend of 30 years, state Sen. Tom Davis, said he didn't know about the affair until Wednesday.
"I think that South Carolinians, in particular Americans, have tremendous capacity for forgiveness. That said, they can also recognize hypocrisy. I think the tale of the tape will be the next few days, whether or not Governor Sanford is sincere in his repentance," Davis told ABC's "Good Morning America" on Thursday.
About three weeks ago, Sanford lost a court battle to reject the federal stimulus money. A few days later, Jenny Sanford kicked him out of their home to begin a "trial separation" with hopes of reconciling.
Then on Monday, lawmakers and reporters started questioning where the governor had been for five days, including Father's Day weekend. His aides said the outdoorsman was hiking the Appalachian Trail to wind down from a grueling legislative session.
But Wednesday the governor held a rambling, tearful news conference in which he finally revealed the truth: "I've been unfaithful to my wife." His family did not attend.
The 49-year-old ruminated on God's law, moral absolutes and following one's heart. He said he spent the last five days "crying in Argentina."
Sanford described the woman as a "dear, dear friend" whom he has known for about eight years and been romantically involved with for about a year. He said he has seen her three times since the affair began, and his wife found out about it five months ago.
Sanford denied instructing his staff to cover up his affair. He said he told them he thought he would be hiking on the Appalachian Trail and never corrected that impression after leaving for South America.
"I let them down by creating a fiction with regard to where I was going," Sanford said. "I said that was the original possibility. Again, this is my fault in ... shrouding this larger trip."
The State newspaper in Columbia published steamy e-mails between Sanford and the woman. Sanford did not identify her, nor did he answer directly whether the relationship with her was over.
"What I did was wrong. Period," he said.
Now the people of South Carolina and national GOP leaders are picking up the pieces.
Davis, Sanford's longtime friend, said he expected the governor to stay in office.
"We're all human, we all have failings and all we can do when confronted with those failings, is to own up to them and acknowledge the hurt you've cause others," Davis told CBS' "The Early Show."
Mississippi Gov. Haley Barbour took over leadership of the Republican Governors Association after Stanford resigned from the post. In little more than an hour after his announcement, other Republicans were backing away from him: the Value Voters Summit dropped him from the lineup for its September roundup of GOP notables.
Political experts expect little from his last 18 months in office, and certainly not with the Legislature he's fought with for years. A lame duck session looms for Sanford.
"Truth be told, over the past few years, he has soured his relationship with the Legislature so much that he hasn't been particularly effective at getting an agenda through," said Scott Huffmon, political scientist at Winthrop University. "And with the stimulus fight, pushing it all the way to the state Supreme Court, that affirmed the governor's subordinate position in this state."
For now, Sanford's looking at the basics.
"Over the time that I have left in office, I'm going to devote my energy to building back the trust the people of this state have placed in me," Sanford said.
It will be a tall task. While some South Carolinians said they appreciated Sanford's eventual candor in admitting to his affair, the tawdry news surprised many.
"I was shocked, shocked," said Tom Daly, 42, a magazine editor in Charleston. "First of all he's a Republican golden boy and he's a strict, staunch conservative. I'm so shocked. It was something I did not expect."