The fastest-growing counties in 2004 were fueled largely by white Americans moving from urban centers to the suburbs and exurbs, which largely explained Bush's dominance then. But Hispanics and other minorities are now driving much of the increase in the fastest-growing places. Obama won 12 of the 15 fast-growing counties with the highest percentage of minority residents, and he won all but one of the eight fastest-growing counties in which whites are a minority of the population.
There is also a significant racial difference in counties in which Obama performed better than Democratic nominees in previous election cycles. In counties where Obama exceeded the average Democratic performance from 1976 to 1992 by at least 10 percentage points, white residents comprised an average of just 59 percent of the population. In counties in which Obama's share of the vote trailed the previous Democratic averages by 10 points or more, whites comprised an average of 76 percent of the population.
Reflecting a decades-long trend of population migration from the Northeast to the Sun Belt, the vast majority of the 100 fastest-growing counties in the United States fall below the Mason-Dixon Line. Eighteen of the top 100 are in Texas, another 14 are in Georgia, and 11 more are in Virginia. Not a single one of the fastest-growing counties is in the Northeast, and only five — one each in West Virginia, Indiana, and Iowa, and two in Kentucky — are in the Rust Belt.
Rapid growth helped Obama put new states into play. Obama performed better than the average Democratic presidential nominee from 1976 to 1992 in each of the 11 counties in Virginia that made the list, by an average of 16 points. (He did best in Falls Church city, where he outperformed his predecessors by 21 points, and he even improved upon traditional Democratic performance in King George County, east of Fredericksburg, by a single point.) Obama ran up big margins in the two North Carolina counties to make the list — Mecklenburg and Wake — improving by double digits on the results for earlier Democratic nominees.
All told, Obama outperformed his predecessors by more than 10 points in 21 of the 100 fastest-growing counties, while McCain beat earlier Republican nominees by 10 points in 20 of the fastest-growing counties. Obama's better performances came in swing states and in heavily Republican territory like Summit County, Utah; Hamilton County, Ind.; and Shannon County, S.D. McCain's best improvements came almost exclusively in red states; he improved noticeably in just one county (in a state that he lost) — Sumter County in Florida, where his score was 14 points better than the average Republican.
McCain did best in the counties with the highest growth rate. He won both counties — Charlton in Georgia and St. Bernard Parish in Louisiana — that grew by more than 10 percent over the past year, and he won 11 of the 15 fastest-growing counties. The smaller the county, the better chance McCain won there: He won 23 of the 34 rapidly growing counties that had fewer than 50,000 people.