In his first television ad for South Carolina’s open 1st District seat, former Gov. Mark Sanford talked about “a God of second chances.”

Tuesday’s primary vote will be the first, but not final, test of whether Palmetto State Republicans are similarly forgiving.

Sanford, a staunch conservative attempting to shake off his infamous “Appalachian Trail” legacy, faces 15 other Republicans on the primary ballot for the special election to represent the coastal, GOP-leaning seat. He is all but certain to come in first, but taking less than 50 percent of votes cast. That will send Sanford, a former three-term congressman, to an April runoff with another Republican.

GOP insiders see the top contenders for nabbing that second-place slot as: attorney Curtis Bostic, state Sen. Larry Grooms, former state Sen. John Kuhn, state Rep. Chip Limehouse and economics teacher Teddy Turner, the son of media mogul Ted Turner.

But with so many candidates in the race, the margin for coming in second is small. Voter turnout predictions range from 30,000 to 35,000, which means anything is possible.

“Anyone who tells you that they have a turnout model or know exactly how this is going to go on Tuesday … is lying,” said Jason Miller, a top Republican strategist who is Sanford’s media consultant and former top aide.

Despite the unknowns, there are some signs that certain candidates have a leg up at advancing.

Limehouse has spent the most — more than $350,000 — on television ad buys as of March 15, according to two GOP media buying sources. But Turner, who has spent about $260,000, was on TV the earliest, airing his first ad in January. Sanford has spent about $175,000.

At the end of last week, Grooms had spent only about $116,000 on TV ads, but he had strong endorsements from two of South Carolina’s Republican representatives, Jeff Duncan and Mick Mulvaney.

In a telephone interview, Duncan said he knows and is friends with a number of the candidates, but he said the one who stood out as a proven conservative was Grooms. Duncan said he was making calls to the district on Grooms’ behalf but would probably save in-district campaigning for the runoff.

“I think he’s on the upswing,” Duncan said on March 15. “I think he’s going to be in the runoff and he may be saving my powder until the runoff and we’ll look to trying help him get across the finish line at that point.”

South Carolina’s political history has shown that the second-place finisher in a GOP primary can win the runoff.

Most recently, in the 2012 Republican primary for the new 7th District, former Lt. Gov. André Bauer came in first in the primary, topping then-Horry County Council Chairman Tom Rice by 5 points. But in the runoff, Rice won by 12 points.

In 2004, Republican Jim DeMint came in second in his Senate primary, only to win the runoff and take the office.

But how well Sanford does on Tuesday may be a determinant of his strength on April 2.

“Look at how well Sanford does in round one,” said Richard Quinn, Sr., a longtime South Carolina GOP strategist who is not involved in the race. “If he gets up over 40 percent in that round, he may have a pretty good shot at winning at round two.”

Sanford supporters think the 40 percent bar is high and expect him to land with somewhere over 30 percent of the vote.

His Achilles’ heel remains his disappearance from the state for days in 2009, when he was governor. He subsequently admitted to having an extramarital affair with a woman from Argentina. He had told his staff he was hiking on the Appalachian Trail.

Few underestimate Sanford’s strong political skills and the electorate’s familiarity with him. But there’s a certain incredulity that permeates longtime operatives’ comments about him winning elected office again.

“He’s talking about a God of second chances,” Quinn said. But if Sanford comes back to Congress, the strategist said with a laugh, “This’ll be more like a resurrection!”

The winner of the GOP runoff will almost certainly face Democrat Elizabeth Colbert Busch, the sister of comedian Stephen Colbert, in the general election. She’s likely to beat frequent candidate Ben Frasier outright on Tuesday.

But she faces an uphill general election climb as a Democrat in a district that is most certainly not. It voted 62 percent for then-Rep. Tim Scott, a Republican, in 2012.

Scott was appointed to the Senate to replace DeMint, leaving his House seat open.