He will be replaced by his chosen successor. Tea party supporters across the country have taken up his messages about fiscal responsibility. Friends say his mid-life crisis is over.
Still, the two-term governor says he's not sure what's next and talks vaguely about writing a book or going back into business.
"It's an interesting spot to be at, because my nature is always to have a next plan, but on this one I don't," said Sanford, a 50-year-old former developer-turned-congressman. All he'll say for now is that he plans to take his son's green pickup truck and head toward home on the state's southern coast, though he's not sure exactly where he'll live.
"I'm driving east on 26 and beyond that, it's a new adventure and we'll figure out the next chapter of life," he said.
The previous chapters include one of the decade's most-watched political implosions.
He disappeared from the state for five days in June 2009 and told his staff he was hiking the Appalachian Trail, but he was really in Argentina visiting his mistress. He returned and held a press conference at which he confessed "I have been unfaithful to my wife."
In lengthy interviews with The Associated Press, Sanford declared his lover his soul mate.
Weeks later, wife Jenny Sanford moved out of the governor's mansion in Columbia with their four sons and into the family's beachfront home near Charleston. The governor did not contest the divorce that followed. She wrote a tell-all memoir, "Staying True," and launched a national book tour.
Meanwhile, Mark Sanford resisted calls to resign, fought an impeachment push and endured a formal rebuke from lawmakers who said he embarrassed the state. He paid a $74,000 ethics fine after AP and other media investigations found improprieties in his flights on state and private aircraft and his campaign spending.
A new round of questions came this spring when Sanford met in Florida with his Argentine lover, Maria Belen Chapur. He later explained he was seeking to rekindle the romance.
"Time will tell," he said in May. "I don't know if it will or won't."
With the end of his term-limited tenure now in focus, Sanford won't talk about Chapur.
"I think I have said more than I ever need to say about my personal life. And in fairness to the people I represent, I'm not talking about it anymore," he said during a recent interview at the Statehouse. "I think anybody would observe the obvious, which is, you know, the events of 18 months ago were, you know, life changing in nature at some level and more than humbling at a lot of different levels."
Sanford hung on after the scandal broke at the urging of friends and allies, including wealthy lawyer and real estate developer John Rainey. He recruited Sanford to run for governor and laments his missed opportunities.
Sanford rose to become chairman of the Republican Governors Association and waged the nation's most visible - but losing - fights against federal stimulus spending. Both sparked talk of a potential 2012 White House run.
"The mishap of June of 2009 just derailed him completely. That cost him the RGA chairmanship and that just shattered his trajectory upward," Rainey said recently. "But I don't think it's over."
Sanford remains well-regarded in conservative circles. In 2006, he was calling for Republicans to get back to their conservative roots. Only a couple of years earlier, he carried piglets dubbed "pork" and "barrel" to the door of the state's GOP-controlled House to protest spending. His persistent warnings about rising deficits and railing against federal mandates fed what would become tea party mantras.
"Clearly, Mark has a future. Equally clearly, I don't know where. A man like that with his talents - and he has talents whether you agree with his political philosophies or not - he's still capable and good and bright," Rainey said, noting former New York Gov. Eliot Spitzer's far more sordid downfall and current gig as a cable news talk show co-host.
During a recent speech to a Rotary club on the coast, a satisfied Sanford told a crowd his final year in office was his best: More budget vetoes were sustained and he won long fights to restructure the state's money-losing employment agency and overhaul sentencing laws.
And Nikki Haley, the legislator he mentored and encouraged, publicly praised him as she clinched the GOP nomination for governor in June. She talked about Sanford's fights on behalf of taxpayers "and his encouragement for me in this campaign. You know, when we talked a year ago, I said, 'Governor, do you think South Carolina is ready for a female governor?' And he said, 'I don't know about that, but they're ready for you."'
Sanford says he'll remain "engaged in the larger war of ideas or the process of politics" at least through writing and possibly working with some conservative think tank. He expects to return to business.
A return to politics isn't planned, he says, "but what I've also learned in life is you never say never."
Longtime Sanford family friend Bernie Kole says the affair was a mid-life crisis and Sanford has moved past it.
"He picked himself up and has taken care of his obligations," Kole said.
Kole introduced Sanford to a crowd of about 100 at a recent Beaufort Rotary Club meeting after giving the governor an application to the club and saying his years of honorary membership and free meals were over.
"But on a personal note, since he is leaving office, I found out he hasn't got a job yet. Does anybody out there have any openings?" Kole asked as the crowd laughs. "Please raise your hands or come up later."