Mitt Romney has slightly better than even odds of winning the South Carolina Republican presidential primary on Saturday. Then it’s on to Florida where Romney currently holds a big lead in the polls and has the largest paid media presence. After Florida comes the Nevada caucus, where Romney and Ron Paul are way ahead of their competitors in terms of organizing local support. If Romney wins on Saturday, his nomination prospects will go from very good to almost certain.

Polls in South Carolina showed Romney with a consistent, if slightly shrinking, lead until Wednesday. Some of the polls released Wednesday showed Gingrich ahead, but Romney continues to hold a slim lead in both the weighted and unweighted polling averages. It’s possible that a surging Newt Gingrich could catch Romney.

Thursday morning brought good news and bad news for Gingrich. The good news? Rick Perry dropped out and endorsed him. Perry’s supporters are staunch social and fiscal conservatives who may be suspicious of Romney. But Perry was polling at only 6 percent. Even a full swing towards Gingrich of Perry’s supporters might not be enough for him to catch Romney. And, of course, Perry’s voters won’t all necessarily go where he tells them to, especially given Perry’s somewhat tepid endorsement. Perry said, “We have had our differences, which campaigns inevitably bring out. And Newt is not perfect, but who among us is? The fact is, there is forgiveness for those who seek God and I believe in the power of redemption, for it is a central tenet of my own Christian faith.” It’s not clear if Perry thinks Gingrich needs divine redemption for his past indiscretions in the realm of politics, his personal life or both. And it is odd to see Perry, who staked his campaign on being a Washington outsider proposing to make Congress part time so congressmen could go home and “get real jobs,” endorsing Gingrich, a former Speaker of the House who consulted for Freddie Mac after leaving office.

The ideal reverberation from Perry’s endorsement for Gingrich would be if some supporters of Rick Santorum see it as a sign that conservatives are coalescing around Gingrich and switch over to his side.

But another event Thursday morning might remind social conservatives why they don’t trust Gingrich. Marianne Gingrich, his second wife, gave interviews to the Washington Post and ABC News about their marriage. Her comments are incredibly damning. She says that Gingrich called her at the home of her 84-year-old mother on her mother’s birthday to ask for a divorce. When they then sought marriage counseling Gingrich admitted to having an affair with his current wife, Callista, and asked for an open marriage so he could continue to cheat on Marianne. At the same time, he was traveling the country giving speeches about the importance of family values. And this is not an isolated incident. Gingrich cheated on and divorced his first wife as well, when she was seriously ill. (If you want to read the definitive piece on Marianne Gingrich, which contains a lot more damaging revelations about Newt, check out Esquire’s article from 2010.) The Gingrich campaign is not contesting Marianne’s version of events.

Romney has sensed the challenge from Gingrich and he has returned to the playbook that worked well at fending off Gingrich the last time Newt surged: attacking Gingrich’s conservative credentials. The Romney campaign has returned to organizing daily conference calls with Romney surrogates, often current and former legislators who served with Gingrich in Congress, calling him “unreliable.” Romney is also running ads to the same effect.

If Romney comes in a close second—and it’s virtually impossible that he’ll come in a distant second—it would hardly be a fatal blow to him. As a formerly moderate Mormon from Massachusetts, Romney was never expected to necessarily win South Carolina. And he has acted accordingly, spreading his resources around elsewhere and jetting up to New York Tuesday night for a fundraiser while his opponents packed in South Carolina campaign events.

Given Romney’s apparent weaknesses in South Carolina—which include not just his religion, home state and past positions but his stiff personality and the fact that his company laid off South Carolina workers—it’s remarkable that he is performing so well here. Here are five reasons why.

Divided opposition. Gingrich and Rick Santorum are competing for the votes of more ardent conservatives, particularly social conservatives. Both of them are on the receiving end of withering attacks on their record from Ron Paul. If you combined Gingrich and Santorum in Nate Silver’s weighted polling average they’d receive 46.8 percent to Romney’s 33.7 percent. If there had been one clear alternative to Romney all along, that candidate might have been able to compete with Romney more effectively. Romney is trouncing his opponents nationally in fundraising and endorsements. Donors and politicians like to back a winner, and the absence of a unified alternative has helped Romney enormously.

Electability. Republicans hate President Obama. South Carolina Republicans especially hate Obama, for the obvious reason. “The hatred for Obama wouldn’t be half as bad if he were white. They think he’s uppity, his wife even more so,” says a staffer for a Republican statewide elected official.

Whether or not you’re motivated by race, you’ll want someone who can win in November if you think Obama is a terrible president. Daniel Farra, 29, a general manager for Applebee’s from Lexington, South Carolina, encapsulates that mindset. He also happens to be the husband of Danyele Gardner, the current Mrs. South Carolina. Farra told me he is supporting Romney because he is “looking for someone who can beat Obama.”

“Realistically, 45 percent of the electorate will vote one way and 45 percent the other, so you need someone who can get that 10 percent in the middle,” says Farra. “Romney, because he is more moderate could do it. Newt maybe could do it because of his intellect.”

South Carolina’s strange affinity for the establishment. The nostrum that Republicans always choose the candidate next in line, typically someone who contended for the presidential nomination before, as Romney did in 2008, is perhaps mostly attributable to South Carolina. Oddballs such as Pat Robertson, Steve Forbes and Pat Buchanan have over-performed in the quirky Iowa caucuses and New Hampshire primary. South Carolina, despite its staunch conservatism, is less amenable to insurgents.

Luck. If Republicans had been able to find a respectable conservative alternative to Romney, South Carolina’s primary campaign would have unfolded quite differently. But instead they were stuck with a group of half-wits, amateurs and has-beens. In the first category, Michele Bachmann and Perry dropped out, as did the unprepared Herman Cain. In the last, Santorum lost his last race by eighteen points and Gingrich resigned as a remarkably unpopular Speaker of the House.

Money. Romney has raised vastly more than his opponents, even during periods when they surged past him in the polls. Romney has used that advantage to buy television and radio ads. He and his Super PAC have spent the most on ads in South Carolina of any candidate. Of course, money isn’t everything. Rick Perry spent the second most in South Carolina.

Here’s one factor that did not much matter: Governor Nikki Haley’s endorsement. Haley is not nearly as popular in South Carolina as outsiders imagine her to be. She beat her Democratic opponent in this heavily Republican state, in a Republican wave election year, by only a few points. She could face a primary challenge when she is up for re-election. Haley’s endorsement certainly did not hurt. She’s an articulate surrogate on Romney’s behalf and it might have helped at the margins. But she has hardly achieved kingmaker status in the state GOP.

Indeed, we know Haley’s touch isn’t golden, because if it were Romney would have South Carolina locked up. Instead, despite all his aforementioned advantages, he could very well lose or end up in a virtual tie with Gingrich.