"The margin is too big to recover from, but state law will still govern the mandatory recount," Grooms said Wednesday. "It's highly, highly unlikely that any errors could overturn a 400-vote margin."
Tuesday was Sanford's first run for office since a 2009 scandal in which he acknowledged an affair. After disappearing and telling his staff he was out hiking the Appalachian Trail, he returned to the state to reveal that he was in Argentina with his mistress. Sanford and his wife Jenny divorced, and he is now engaged to the Argentine woman.
"Are you ready to change things in Washington?" Sanford, flanked by his four sons, asked a boisterous crowd at a restaurant in Charleston's historic district. "I'm incredibly humbled by the outpouring of support we have seen tonight."
Earlier Tuesday, Sanford said it was "a treat and a blessing" to be back on the ballot. He represented the district in Congress for three terms before he was elected governor, serving two terms.
"We all hope for a second chance. I believe in a God of second chances," Sanford said after voting Tuesday.
Whether against Sanford, Grooms or Bostic, Colbert Busch would appear to have an uphill battle in the May 7 special election in the strongly Republican district.
Last fall, Mitt Romney won the conservative district by 18 percentage points, although he beat President Barack Obama by 10 percentage points statewide.
The district reaches from the sea islands with million-dollar oceanfront homes northeast of Charleston to southwest along the coast to the gated communities of Hilton Head Island, with its many Yankee transplants. When Sanford ran in the 1990s, the district reached into more conservative Horry County, but that area has been split and is now part of another district.