The scenario I laid out yesterday came to pass in South Carolina, with John McCain emerging victorious against a conservative field divided three ways, a field that was two parts Huckabee, one part Thompson, and one part Romney. Had just 20% of Mitt Romney’s voters voted tactically for Mike Huckabee, McCain would have been denied this needed momentum boost going into Florida and probably the nomination.

Despite the different actors and alliances in different states, we are beginning to see the real dividing lines of this campaign. It’s the battle of the moderates (McCain), metro conservatives (Romney), and rural conservatives (Huckabee). Stripped of all other hangers-on (Fred, and increasingly, Rudy), nationwide this divide seems to work out to about 40-40-20, or 35-40-25. Conservatives ought to be winning this battle, but Huckabee’s lock on the rural vote (just 16% of the vote in Charleston County, btw) will prevent any kind of clear two-man race before February 5th. Every day that Huckabee’s nice guy act is allowed to continue is a gift to John McCain — and he knows it.

Mitt Romney is fast becoming the candidate of conservatives in the suburbs and the exurbs. In Michigan, he dominated Oakland and Macomb counties with 46% of the vote in a multi-candidate field. In Nevada, he won most convincingly in Clark County. In Iowa, he did better in Des Moines than elsewhere in the state.

The Romney and McCain coalitions also overlap. They represent two different sides of the establishment coin, with McCain representing an older, mainline establishment — the Republican Party of Gerry Ford, Howard Baker, and Bob Dole — and Romney representing the brasher, post-Reagan establishment that was built on the tax issue and whose alliance with modern-day Huckabee voters allowed them to take control of the party in 1994.

Though vastly different in terms of ideology, the Romney and McCain people are still both the establishment — and they alternate control of state chairmanships, RNC seats, county committees, etc. It is perhaps not so surprising that the McCain camp reported that 45% of Romney “ones” in New Hampshire were also McCain “twos.” At the end of the day, McCain and Romney voters look more like each other than they do the Huckabee vote.

Tonight, the Romney and McCain vote at the county level in South Carolina was positively correlated at a mild but statistically recognizable level of 0.16 — a sign of their mutual strength in coastal resort counties. Both McCain and Romney overperformed in key establishment subgroups: Romney did better with pro-choice voters than pro-life voters, he pulled nearly twice as many votes among those not born in South Carolina (a key group for McCain in 2000 that he won more mutedly tonight), and also finished second amongst non-Evangelical voters, which McCain dominated. Despite all this, Romney did better amongst conservatives than non-conservatives, which by process of elimination leaves him particularly strong with the more secular, fiscally minded right.

The trouble for McCain is although he has probably secured the moderate berth in the finals (sorry, Rudy), he hasn’t made many inroads with the base and his vote still looks decidedly unlike what that of a GOP nominee should look like. To say that conservative South Carolinians somehow embraced McCain is to ignore the fact that McCain lost conservatives, pro-lifers, and Evangelicals, and eeked it out against the most divided field to date.

With Romney’s suburban base secure, for McCain to start racking up victory margins in the 40s — which he’ll need as candidates fade or drop out — he’d need to add votes from the Christian conservative base — from supporters of walking wounded like Huck and Fred. Because of their candidates’ personal animosities towards Romney, that is a distinct possibility that such an alliance could be forged — but it would be an alliance of opposites — of pro-life and pro-choice, of liberal and conservative, of secular and evangelical. I don’t know if conservatives are going to overlook that fact.

In the traditional middle of this fight is Mitt Romney, who strives to represent a sort of Goldilocks conservatism. The question is if center is big enough to hold this year.

On to Florida.