Sometime after Jenny moved out, when Sanford thought he couldn’t get any lower, Nikki Haley, then a little-known state legislator making a long-shot bid for governor, appeared at his office. She settled into his red sofa and took out a manila envelope bearing a Post-it with the word “promises” scrawled on it. It contained a letter with a pledge Sanford made to her several months earlier. While still riding high, he persuaded her to run as his successor by vowing to put the full force of his popularity and fund-raising network behind her.

But now he was no longer able to raise money, and his public embrace was a liability. After his collapse, she was languishing in fourth place with relatively little cash. But according to Sanford and others close to him, she and her advisers had another idea for how to jump-start her campaign. Sanford’s political accounts were still flush, and he says she asked him to devote several hundred thousand dollars to a media campaign supporting her candidacy. He says he initially declined. “My gut is, ‘No, you don’t give somebody that kind of money,’ ” Sanford told me. But, he says, she and a top strategist continued to press. And, no longer certain of his own political instincts, he finally deferred to advisers who said fulfilling the request was the right thing to do, given his inability to deliver the way he said he would.

In May 2010, a month before the primary, a nonprofit group, ReformSC, formed at the start of Sanford’s tenure to promote his policy agenda, began a $400,000 ad campaign promoting Haley as “South Carolina’s new conservative leader.” Quickly, Haley moved into first place. In her book, “Can’t Is Not an Option,” Haley credits those ads with moving her poll numbers but only describes asking Sanford to make phone calls.

As an issues group, ReformSC was limited in its ability to participate directly in political campaigns and was prohibited from coordinating with them. The spot did not technically call for Haley’s election — it focused on her role in championing a bill to end anonymous statehouse voting — but a judge called a temporary halt to the ads after an opponent and some ReformSC donors filed a lawsuit charging that the commercial was a thinly veiled, illegal campaign spot. (Governor Haley’s office sent an email in mid-June emphasizing that the ads were about “a key reform supported by Governor Sanford and then-State Representative Haley.”) Most of the ads had run by then anyway, and Haley soon drew a closing endorsement from Sarah Palin that sealed her victory.

In what is described by friends as the slight that bothered him the most, Haley never personally let Sanford know that she appreciated what he did for her. “She never thanked him,” said John Rainey, a prominent South Carolina businessman and power broker who has been a confidant of Sanford’s since his first run for governor. Not in a written note, not in an email, not verbally, Rainey said. “He’s still upset by it. That’s something you never forget — ingratitude.”

About a year later, the former governor set aside his pride and asked the new governor if she could spare one of her University of South Carolina football season tickets so Sanford’s oldest son could see a game; he also asked if his son and a couple of high-school friends could have an al fresco meal on the grounds of the mansion, his childhood home. Sanford has told friends that her office balked at the ticket and declined to provide a meal.