Here at Facing South, we write a lot about how the South's rising social and economic clout -- and therefore its national political importance. In yesterday's Wall Street Journal, Michael Barone has an interesting piece on population shifts in the U.S., which adds an interesting new wrinkle to our understanding of where people are moving today and what it means.

Barone echoes the well-known theme that "population has been flowing from the Snow Belt to the Sun Belt, from an industrially ailing East and Midwest to an economically vibrant West and South."

But he takes it one step further, looking at what kind of cities are growing in size and stature. Looking at the 2000 Census and estimates for 2006, and groups who is losing and who's gaining into four categories:

COASTAL MEGALOPOLISES: This is New York, Los Angeles, San Francisco, San Diego, Chicago (on the coast of Lake Michigan), Miami, Washington and Boston. As Barone writes, "The bad news for them is that the Coastal Megalopolises grew only 4% in 2000-06, while the nation grew 6%. Coastal Megalopolitan states ... are projected to lose five House seats in the 2010 Census, while California, which has gained seats in every census since it was admitted to the Union in 1850, is projected to pick up none." The only balancing factor is immigration.

INTERIOR BOOMTOWNS: People are flocking to these areas, and the South is benefiting most from this trend:

The nation's center of gravity is shifting: Dallas is now larger than San Francisco, Houston is now larger than Detroit, Atlanta is now larger than Boston, Charlotte is now larger than Milwaukee. State capitals that were just medium-sized cities dominated by government employees in the 1950s -- Sacramento, Austin, Raleigh, Nashville, Richmond -- are now booming centers of high-tech and other growing private-sector businesses. San Antonio has more domestic than immigrant inflow even though the border is only three hours' drive away. The Interior Boomtowns generated 38% of the nation's population growth in 2000-06.

Barone sees two other broad categories, the RUST BELT, including Detroit, Pittsburgh, Cleveland, Milwaukee, Buffalo, Rochester, which have all lost population since 2000, and what he calls STATIC CITIES, places that aren't growing or losing, which are all over the country: Philadelphia, Baltimore, Hartford Seattle, Denver, Portland, Minneapolis, St. Louis, Cincinnati, Kansas City, Columbus and Indianapolis.

What are the political implications of all this? As Barone correctly points out:

[T]he Interior Boomtowns voted 56% for George W. Bush in 2004. Texas, Arizona, Florida, Georgia and Nevada--states dominated by Interior Boomtowns--are projected to pick up 10 House seats in the 2010 Census.

The growing political dominance of the South and West is indisputable. But Barone's implication that growth in Southern "Interior Boomtowns" will be a boost for Republicans doesn't necessarily follow.

Who's moving to the South? A big factor are Latino immigrants -- and 57% of Southern Latinos voted Democrat in 2006. As for migrating whites, they are largely mid- to upper-class -- but they are also moving from Blue State political environments.

We know the South is growing, and with it the South's political clout (yet more reason that no party can seriously talk about "writing off the South" -- especially with the 2010 Census right around the corner). The question is, will newcomers be changed by the South -- or will they end up changing it?

I would argue that the commitment of political parties and organizations to investing in the South will play a big role in determining which way the booming South turns.