The gist of Barone's analysis is that the southward and westward internal migration of the previous decades has been altered to migrations from the East and Left Coasts inland. The link above has the details.
Domestic inflow has been a whopping 19% in Las Vegas, 15% in the Inland Empire (California's Riverside and San Bernardino Counties, where much of the outflow from Los Angeles has gone), 13% in Orlando and Charlotte, 12% in Phoenix, 10% in Tampa, 9% in Jacksonville. Domestic inflow was over 200,000 in the Inland Empire, Phoenix, Atlanta, Las Vegas and Orlando. These are economic dynamos that are driving much of America's growth. There's much less economic polarization here than in the Coastal Megalopolises, and a higher percentage of traditional families: Natural increase (the excess of births over deaths) in the Interior Boomtowns is 6%, well above the 4% in the Coastal Megalopolises.
He goes on to say that Florida will probably have the same number of electoral votes in 2012 as New York, Arizona will have 12 to sixteen for Barone's native state of Michigan. All in the last sixty years. And besides domestic inflow, the "natural increase" of children being born is far higher in the internal heartland areas which are predominantly Republican.
Finally, a quibble. Barone puts Miami in the coastal megalopolis category, but Miami has an outflow of 2% and an inflow of 8%, making it perhaps the only coastal city to thrive over 2000-2006. Since they switched parties in the past decade, Florida and Texas are fast becoming natural Republican bases, if Barone's analysis is correct and voting patterns persist. And both will get more CDs---hence electoral votes---when the 2010 census verifies the various data bases Barone employs for his article.
Meantime, I am looking for the latest edition of Barone's Almanac of American Politics which is the single best book for understanding the rich variety of America's political base.