The basic dynamics of the 2012 GOP nomination battle remain unchanged: the bulk of the GOP electorate doesn't want Mitt Romney, but isn't really sold on an alternative. Iowa's voters broke late to Rick Santorum as the conservative alternative; South Carolina's broke late, and much more decisively, to Newt Gingrich. It remains up to Newt now to prove he can hold together the conservatives going forward, as Santorum was not equipped or financed well enough to do.
It's worth noting here the raw numbers. While the categories don't perfectly describe the candidates or their supporters, it has been generally true that Romney and Jon Huntsman have appealed to the more moderate Republican primary voters; Gingrich, Santorum, Rick Perry and Michele Bachmann to the more conservative voters; and Ron Paul to the libertarian voters. What we see in the first three states is that in South Carolina, as in Iowa, the conservative vote was a majority:
Iowa: Conservatives 53%, Moderates 26%, Libertarians 21%
New Hampshire: Moderates 56%, Libertarians 23%, Conservatives 19%
South Carolina: Conservatives 57%, Moderates 28%, Libertarians 17%
There will be other states - possibly including delegate-rich California and New York - that will more nearly resemble New Hampshire's profile; there will be states where Newt is not on the ballot (Virginia), where Romney has a home-field advantage (Michigan, Massachusetts, Utah), or where the confluence of caucuses and a large Mormon population favors Romney (Nevada). But at the end of the day, regardless of desperate efforts to prop up Santorum, it is hard to see any of those structural/organizational factors overcoming the core question: either Newt will unite the conservative vote, or Romney will have to earn a share of it away from him. Which has always been how we needed to pick a nominee. However you describe the GOP "Establishment," our nominee can and should only be one whom the primary voters - however reluctantly - have decided after reflection and stress-testing to nominate.
Florida won't be the last test of this, given Romney's money and organization advantages there, but it will be the first serious one. In Churchill's phrase, South Carolina was not the end, or the beginning of the end; it marked the end of the beginning.