CHARLESTON, S.C. -- One of Mitt Romney's top surrogates, former New Hampshire Gov. John Sununu, began the process Friday morning of managing expectations in the event of a possible Romney loss to Newt Gingrich in Saturday's South Carolina primary.

Sununu predicted that the GOP nomination fight will run through every primary and caucus state, all the way to the summer.

"I think you're going to see the same kind of long slog that you saw in '76, with [Gerald] Ford and [Ronald] Reagan, that it took the whole thing to win," Sununu told reporters.

"This is a long slog," Sununu said. "[Romney]'s never suggested one or two or three primaries or caucuses would make the difference. The whole campaign has been designed to go through the long slog."

Asked what Romney, the former governor of Massachusetts, will need to do if Gingrich beats him in South Carolina, Sununu responded, "He has to do what they intended to do from the beginning: slog along."

"Mitt Romney's strength has been clearly defined as being ready for a long campaign under the new rules," Sununu said.

Sununu's comments are the clearest indication that the Romney campaign is preparing for a possible loss here Saturday, as Gingrich, the former House Speaker from Georgia, rides a wave of momentum based on his debate performances this week.

It is, in effect, the first move by the Romney campaign to blow up the bridge marked "Early Primary Win" and to retrench further back inside its campaign fortress, where it is in fact prepared and ready for a long primary. The campaign has been organizing in many of the early primary and caucus states for months, and has the organizational capacity and the money to fight until the end.

This is not to say that Romney can't win Saturday. The state of the race is still highly fluid less than 24 hours before polls open. But if he does in fact get defeated by Gingrich's burst of momentum, Romney's campaign will have begun laying the groundwork for its damage control.

Romney's nightmare scenario is one in which Gingrich wins South Carolina and gathers so much momentum from his victory that he goes on to win Florida on Jan. 31 and becomes something of a frontrunner. Even if that were to happen, though, the month of February will present new challenges for Gingrich.

Four states will hold caucuses in early February, and they will likely be dominated by Romney and Rep. Ron Paul (R-Texas), both of whom have been organizing in those states. After those, the next contests will not occur until Feb. 28. Whether or not Gingrich gathers momentum during the month, then, depends more on his campaign's messaging than it does on voters.

During that long stretch of dead time, the Romney campaign is confident that it can essentially persuade Republicans that Gingrich is what they have argued he is this week: an unreliable and unpredictable human being who cannot be trusted with the presidency. They fully expect Gingrich to help them make that case, by making comments or behaving in a way that demonstrates his lack of discipline.

"He is a ticking time bomb," said Henry Barbour, a top Republican party fundraiser from Mississippi who moved his support to Romney from Texas Gov. Rick Perry after Perry dropped out on Thursday.

"He won't last. He's great for a cable news show, but when does he blow up? Not what we need for a president," Barbour told The Huffington Post. "Romney has the plan, infrastructure and resources to win a quick or protracted campaign. Gingrich and [former Sen. Rick] Santorum will have a very hard time managing this as the pace quickens beyond their ability to execute in all the places they need to campaign. It's a brutal process."

Sununu batted down speculation by MSNBC's Joe Scarborough that Republican party insiders are so worried by Romney's weaknesses as a candidate that they are discussing the possibility of a brokered convention, where the party chooses a different nominee in late August.

"Joe's been drinking too much coffee on his morning show. I haven't heard a single responsible person in the Republican party say anything like that," Sununu said.

UPDATE: 2:00 p.m. -- Mitt Romney sought to manage expectations during a Friday availability with reporters in Gilbert, saying he hopes to win South Carolina but that the state is an "uphill battle."

"Well, we have a long process ahead of us, 1,150 delegates to get. I sure would like to win South Carolina, but I know that if those polls were right, regardless of who gets the final number, we're both going to get a lot of delegates. I want as many delegates as I can get -- I want the most delegates coming out of South Carolina. But I don't know what the numbers will be," he said.

"I’m pretty confident, cautiously optimistic," he continued. "When I look at the crowd this morning, my enthusiasm meter went up, my confidence goes up. But we'll see what the numbers are in the final tally. But what I can tell you is this is a campaign that is gonna go the distance, I'm confident we’re gonna get the delegates we need and that despite all of the ups and downs of the campaign, in the final analysis, if I do my job right, get our supporters motivated, why we'll be able to take the prize."

"I think I was tested in Iowa in a major national way. I think I was tested in New Hampshire in a major national way and I'm going to be tested here, Florida, Nevada, Michigan. And I think I said from the very beginning South Carolina is an uphill battle for a guy from Massachusetts. I knew that. We're battling hard. The fact is right now it looks like it's neck and neck that's a good spot to be in. I'm pretty pleased and pretty proud about the success of our effort."

Elise Foley contributed reporting from Gilbert, S.C.