Since 1980, a Southerner has finished first or second in every Iowa Republican presidential caucus.

More than 40 percent of John McCain’s voters in 2008 were from the South. Thirty-six percent of Republican National Convention delegates will come from the region. …

If a candidate dominates the South — and it’s much easier for a Southern candidate to do that — he’ll have made a lot of headway into winning the votes and delegates that he’ll need to secure his party’s nomination. Certainly there have been regional and factional candidates — think George Wallace, for example — who did well in the South but poorly elsewhere. But a candidate like Mr. Perry, who would have advantages like fundraising and establishment support that would extend to all corners of the country, might be more like Bill Clinton and George W. Bush, doing very well in the South and still well enough outside of it to win his party’s nomination. …

For a Republican candidate, in fact, this advantage may be especially powerful because of a demographic quirk related to Iowa, the first and most important state in the nominating process. Some 60 percent of Iowa Republican voters are born-again Christians — about the same fraction as in many Southern states. That’s why Southern Republicans have done so well in the state.