Having made significant gains in statewide races on Nov. 2, Republicans are in an advantageous position for the Congressional redistricting process that will take place between now and the 2012 elections. That process will kick off later today when the Census Bureau announces the first set of results from the 2010 Census, including which states will gain or lose seats in Congress (and consequently, votes in the Electoral College).
Even before the midterm elections, though, Republicans were poised to gain seats in the next Congress for another reason: under the old boundary lines, which first went into effect in 2002, their Congressional districts tended to grow faster than Democratic ones.
Nine Congressional districts, for instance, had populations of 900,000 or more as of 2009, according to Census Bureau estimates, while the average Congressional district has about 700,000 people. All nine — as well as 17 of the 20 most populous districts over all — elected Republicans to the U.S. House in November. That means that the Republicans will, in many cases, have the luxury of both protecting their incumbents in these districts and spreading out their excess voters to neighboring districts to make them easier to win.
Essentially all of the fastest-growing districts are in inland areas south of the Mason-Dixon line, or are west of the Continental Divide. Many are in areas that demographers describe as ‘exurbs’: newly developing areas that are located relatively far — perhaps a 30- or 60-minute drive — from cities like Phoenix, Dallas, Houston, Las Vegas, Charlotte or Atlanta, and that attract an upscale mix of commuters, families and retirees. Although most major American cities are no longer losing population — on the contrary, at least 20 of the 25 largest cities are likely to have gained population in the 2010 Census compared with 2000 — they are not growing as fast as the exurbs, and therefore stand to lose proportionally, because the number of seats in Congress is fixed.
http://fivethirtyeight.blogs.nytimes.com/2010/12/21/exurban-growth-should-bolster-g-o-p-in-congressional-redistricting/