Gallup’s analysis of the reapportionment results are not necessarily a big surprise — and perhaps worse for Democrats than this shows.  Based on Gallup’s surveys earlier in the year on party identification, they note that all of the ten states that lost representation in the House have overall Democratic affiliation advantages.  Five of the eight gainers have GOP affiliation advantages:

Over the years, relative changes in population across the states have resulted in extraordinary shifts in political power. The traditionally Democratic state of New York, for example, has gone from 45 congressional seats after the 1940 census to 27 seats after the 2010 census. On the other hand, Texas, in recent decades a reliably Republican state, has gone from 21 to 36 seats during the same time frame.

Nine of the 10 states that lost congressional seats as a result of this year’s census are in the Northeast or Midwest. The exception is Louisiana, whose population loss at least partly as a result of Hurricane Katrina cost it a seat. Politically, all 10 of these “losing” states skew Democratic in political orientation, based on Gallup’s latest state political identification data from January through June of this year. The two states that each lost two seats, Ohio and New York, have a net Democratic political identification of +7 and +19, respectively. The Democratic margin in the other eight losing states ranges from +20 in Massachusetts to +1 in Missouri.

The eight states that gained congressional seats this year present a more mixed political picture. Texas was the big winner, gaining four seats as a result of its extraordinary growth from a population of almost 21 million in 2000 to 25 million in 2010. Texas has a net Democratic party identification of -3, meaning that more Texas adults identify as Republicans than as Democrats. On the other hand, Florida gained two seats, and has a net Democratic identification of +4. Party identification skews Republican in four of the remaining six states, all of which gained one congressional seat, ranging from a -32 net Democratic margin in Utah (Utah is the most Republican state) to -3 in Georgia. Both Nevada and Washington have net positive Democratic party identifications.

While the states’ party affiliation breakdowns may have favored Democrats, at least a couple of the 10 have traditionally supported Republicans in presidential elections.  Ohio went to Obama in 2008 and Missouri almost did as well, but both states went heavily Republican in the 2010 midterms.  Louisiana had been mostly Democratic in state elections but was fairly reliably Republican in presidential contests; McCain won Louisiana in 2008 by eighteen points.  For that matter, even one of the supposed Democratic gainers, Florida, went heavily Republican in the midterm after going for Obama in 2008; Florida also narrowly went Republican in both of George W. Bush’s elections, and Bill Clinton only won it once (1996) with less than 50% of the vote.

Incidentally, this does tend to negate one argument after the reapportionment was announced.  Some has framed this as a challenge to Republicans because of the nature of the population growth, ie, the more rapid increase in non-white population.  However, these changes didn’t just happen in the final months of the decade between the two censuses.  Even after all of the population change and movement, Republicans won a resounding victory in the 2010 elections, and not just on the national level.  The GOP also picked up a record number of seats in state legislatures in this election, flipping almost two dozen chambers across the country.  That came at the end of that migration and growth, not at its beginning, which means that the changes don’t appear to have disadvantaged Republicans at all.

Michael Barone’s analysis probably comes closest to the truth: low-tax states attract larger populations, while high-tax, high-regulatory states tend to lose people.  That also works in the GOP’s favor, and explains why it resulted in such a resounding win in these midterms.

Update: Missouri went to McCain by a very narrow margin in 2008 — fourteen one-hundredths of a point.  I originally had Missouri as going for Obama in this post.