Donald Trump is the favorite to win South Carolina, in the estimation of the state's former GOP governor, but he needs to prepare for a vicious political fight with his rivals.

"There'll be some rip-your-face-off ads, I have no doubt, that wouldn't play in New Hampshire, wouldn't play in Iowa, but it'll play in South Carolina," Rep. Mark Sanford, R-S.C., who served as governor from 2003 to 2011, told the Washington Examiner. "And so, as a consequence, I think that unless Trump is able to defy all political conventions, some of those will have a degree of effect. That's why I think the field will end up tightening."

Trump leads the field by a wide margin in South Carolina, but Sen. Ted Cruz, R-Texas, has a firmer grasp on second place than anyone did in New Hampshire in the run-up to that primary. And although the mainstream Republicans and evangelicals tend to perform well, which could help Cruz, Sanford suggested that the poor state of the economy in recent years gives Trump a leg-up.

Sanford suggested that Trump won't have to absorb the brunt of those negative attacks, though. Rubio and Bush regard each other as mortal threats. The Florida senator's team, notably, includes the political operatives who reportedly spread rumors during the 2010 gubernatorial race that Nikki Haley had had an affair. Warren Tompkins, who leads Rubio's super PAC, led George W. Bush's South Carolina operation in 2000, when Sen. John McCain was falsely accused of having a black child out of wedlock (McCain and his wife adopted the girl).

"If history is any prologue, then I think it would say it hasn't exactly accrued to anybody's benefit to go after Trump, therefore [a candidate might think] 'I may leave him alone and I'll go after the other guys because all I need to do is come in number two and I'm in a good spot going into the next round," Sanford said.

Trump is performing well in upstate South Carolina, the home of the evangelicals who boosted Mike Huckabee's near-win against John McCain in 2008. Sanford attributes that, in part, to the economic struggles that have hit the area of late.

"You see the textile industry ... as textiles changes, some people were able to get jobs at BMW, great jobs, in modern and advanced manufacturing," Sanford said. "But a number of people weren't and that group of folks is part of the fuel that's fueling the Trump phenomenon."

Cruz could also do well in that region, however. Jeb Bush and Sen. Marco Rubio, R., Fla., can also compete for the evangelical vote. Prior to the New Hampshire debate, Sanford regarded Rubio as the likely third contender, but now he suspects that Bush could be in a stronger position. "South Carolina has been good to the Bushes over the years," he said.

Trump is currently first in the Washington Examiner's presidential power rankings while Cruz is second.