What happens now? Mitt Romney will win New Hampshire next Tuesday, there’s little doubt about that. There is some drama around the question of how well or poorly Rick Santorum does there. But I think that the real action will take place in South Carolina, which holds its primary on Saturday Jan. 21. If Santorum is going to trip up Romney, it’s going to happen there. And unlike Iowa, which has a spotty record of picking winners, South Carolina is a perfect 8-0 since 1980—every Republican who has won this primary since it was moved up to be the “first in the South” primary has gone on to win the nomination.

First, let’s talk New Hampshire. In a poll I saw on CNN Tuesday night, Romney was at 47 percent, while Santorum was at 10. But his support had doubled in a matter of days. Ron Paul had 17 percent, Jon Huntsman 13 percent, and Newt Gingrich 9. I would assume that Paul loses a couple of points but keeps most of his total, say 15. Maybe a good chunk of Gingrich’s vote shifts to Santorum. But that still doesn’t make it remotely close. The media might decide that Santorum, to keep it respectable, needs to finish ahead of Huntsman. Santorum also has to give thought to how hard he’s going to compete in the state, because if he goes all-out and gets spanked by 30 points, his balloon will burst quickly, and the race will be over.

But say that Santorum does perform respectably there. His campaign is being managed by the same guy who ran Pat Buchanan’s 1996 insurgent win, and Santorum does have a number of endorsers in the state. He’ll likely emphasize the economic, let’s-care-about-manufacturing aspect of his platform and downplay the Kulturkampf stuff. With Gingrich tagging along calling Romney a liar, it’s not hard to envision Santorum doing just well enough.

Then the action moves to South Carolina, which will be totally pivotal. I’m sure the polling firms are furiously in the field down there now, and we’ll be seeing new numbers from there later this week. But as of this writing, there are no recent polls. At realclearpolitics.com, the most recent public polls go back to mid-December, and Gingrich led those with percentages in the 30s. Santorum was barely above asterisk levels. We’ll obviously get a different read this week. Gingrich will surely sink. Rick Perry insisted in a Wednesday tweet that he’ll campaign there, but after his pathetic showing in Iowa, one doubts he can really expect much support in the Palmetto State. He and (dropout) Michele Bachmann added up to about 14 percent in these polls. But how different will the new polls be? That’s the interesting question.

Santorum’s status in these new polls will help us answer what is, to me, the key question about him now: is he a compelling enough character for huge numbers of conservatives who favored a different candidate to do a quick about-face and decide, "OK, he’s my guy"? I’m not sure he is. He was the last of the red-hot righties for a reason to get his 15 minutes—he just doesn’t have much personality. On the other hand, his speech Tuesday night was excellent, I thought. The C. S. Lewis quote (points for high-class dog whistle!), the hug and kiss for the wife, the God-is-my-friend trope, the story about his little daughter with the malady, which even had me welling up . . . he put it all out there rather nicely from the Christian conservative point of view. It was one of the deftest such speeches I’ve ever seen. There may be more within the guy than people think.

Romney has been at 20 percent or so in South Carolina. Santorum, benefiting from the lion’s share of Gingrich’s, Perry’s, and Bachmann’s support, should be in that ballpark, which could make the state winnable. Of course, he also has to be able to withstand the attacks. If South Carolina has meant anything in the past, it has meant that. (Think of the calumnious allegations against John McCain in 2000. This is why people call South Carolina the “firewall” state for frontrunners. And Romney not long ago secured the backing of new governor Nikki Haley, meaning that the state’s Republican establishment will be with him. Even if they don’t love Romney, they’ll presumably work hard to get him the nomination-ensuring win just to keep their records intact.

But Haley is not popular. She’s been a terrible governor and is lucky to have an approval rating in the mid-30s. And she’s not disliked just by moderates and whatever liberals exist in the state. Some Tea Party leaders feel betrayed by her endorsement of Romney, and they’re even talking of challenging her from the right when she runs again. There appears to be a sense that Haley is angling for personal glory and using her office toward that end. So there is clearly some anti-establishment sentiment on the right.

New Hampshire will matter. It always does one way or another. But all signs point toward South Carolina as pivotal, the rubber match after a strong Santorum performance in Iowa and a clear Romney win in New Hampshire. That’s why.