By Greg Giroux, CQ Staff

Geography is destiny when it comes to political clout in the U.S. House of Representatives. The 435 House seats will be reapportioned based on the 2010 population census, to be conducted in just a bit more than two years, with several faster-growing states gaining greater congressional representation in the next decade at the expense of some of the slower-growing states.

Since reapportionment results in shifts of power to come at the end of the decade, state officials anxiously await the annual population estimates released year-end by the U.S. Census Bureau. And the latest version for 2007 makes it clear that the next official set of population numbers will extend the long-standing pattern of gains for the “Sunbelt” regions of the South and West, and away from the once-dominant industrial and agricultural bastions in the Midwest and Northeast.

Six states — all in the Mountain West and South — would gain House seats if the reapportionment were actually performed today, according to an analysis released Thursday by Election Data Services Inc. The consulting firm’s calculations were based on the Census Bureau estimates of the 50 states’ populations as of July 1, 2007. This chart compares each state’s population in 2000, when the last census was taken, with its 2007 estimate.

Election Data Services found that Texas would gain two seats and Arizona, Florida, Georgia, Nevada and Utah would gain one seat apiece if the reapportionment were performed using that Census data. This perpetuates the robust growth already seen among these states. Every one of them gained at least one House seat in the 2000 reapportionment with the exception of Utah, which just very narrowly missed winning an additional seat.

Balancing the ledger are the states that would lose seats. Seven states — Iowa, Louisiana, Massachusetts, Missouri, New York, Ohio and Pennsylvania — would lose one seat apiece if the most recent Census data were used to perform a reapportionment today, according to Election Data Services. Ohio last gained a seat in the 1960 reapportionment but has lost seats in each of the past four distributions; the other six states reached their apex in congressional representation before World War II.

Pennsylvania, which was awarded 36 House seats in the 1910 reapportionment, would have a House delegation half that size if it loses one of its 19 current House districts in the 2010 reapportionment. It seems certain that will happen.

Louisiana is the one Southern outlier in this group of states otherwise located in the Northeast and Midwest. Slower-than-average economic and population growth early this decade had Louisiana on the brink of losing one of its seven House seats — then came Hurricane Katrina in 2005, causing population displacements that virtually guarantee that the state will be down one after the next census.

Those gain-and-loss figures are far from set in stone, however. In fact, Election Data Services came up with a strikingly different House seat calculation after extrapolating the 2010 state-by-state populations — the figures that will be used to perform the official reapportionment — using three different scenarios of population growth: a “long term” trend model that predicts the 2010 state populations based on shifts from 2000 through 2007; a “mid-term” trend model that takes into account population shifts during the period from 2005 to 2007; and a “short-term” trend model that uses estimated population changes within the past year only.

By any measure, Texas emerges as the biggest winner in the 2010 reapportionment. Under all three scenarios, its gain after the census would jump four House seats, bringing the state’s allotment to 36 seats from its present 32. Texas, which was given two seats in the first reapportionment after it became a state in 1845, has gained at least one House seat in all but one of the 14 reapportionments performed since 1850.

In the early 1990s, Texas became the nation’s second most populous state, surpassing New York and trailing only California (where the rate of population growth has slowed after explosive gains in decades following World War II).

All three population projection models have Arizona gaining two House seats (up to 10 from its present eight) and Oregon gaining one seat, up to six from its present five. Under two of the three projections, Florida would gain two seats (pushing its delegation up to 27 seats) and North Carolina and South Carolina would gain one seat apiece, for totals of 14 and seven respectively.

All three models assess losses of two seats each to New York (which would drop to 27) and Ohio (down to 16) and one seat apiece to Illinois (down to 18 seats), Michigan (14) and New Jersey (12).

The Web site of the U.S. House historian provides a chart that lists the number of U.S. House seats that have been apportioned to states over the years.

The 2010 reapportionment will presage the state-by-state congressional redistricting processes that will ensue in 2011 and 2012, which will be controlled by legislatures and governors in most states. A state that loses one or more U.S. House districts will have to craft a map that reflects politically difficult choices about which districts to merge. In states that gain House districts, look for legislators in at least some states to be integrally involved in the line-drawing process to facilitate their own election to Congress.

The 2010 reapportionment also will influence three presidential elections, in 2012, 2016 and 2020. That is because each state’s allocation in the Electoral College — the process by which the United States elects the president every four years — is the sum of its seats in the U.S. Senate, where each state has two regardless of population, and the U.S. House, which is apportioned according to population. The one exception is the District of Columbia, which has never been given full congressional representation, and is thus unaffected by reapportionment, but has three electoral votes, the equivalent of the nation’s smallest states, under the 23rd Amendment to the Constitution that was ratified in 1961.

If the 2004 presidential election were replayed under the estimated 2007 reapportionment of House seats, President Bush would have received 289 electoral votes, three more than the 286 he actually received, with 270 needed for a majority. Bush won all six states that would gain a cumulative seven House seats in a 2007 reapportionment. He also won four states — Iowa, Louisiana, Missouri and Ohio — that would lose one seat apiece if the reapportionment were performed today using current Census Bureau figures.

The following is a summary of the major findings in the report released by Election Data Services. The full report is available here.

If a reapportionment was performed using Census Bureau population estimates of the 50 state populations on July 1, 2007

• Gainers (6 states, 7 districts): Texas (2), Arizona (1), Florida (1), Georgia (1), Nevada (1), Utah (1)

• Losers (7 states, 7 districts): Iowa (1), Louisiana (1), Massachusetts (1), Missouri (1), New York (1), Ohio (1), Pennsylvania (1)

If a reapportionment was performed using projections of the 2010 state populations (long-term trend model)

• Gainers (7 states, 12 districts): Texas (4), Arizona (2), Florida (2), Georgia (1), Nevada (1), Oregon (1), Utah (1)

• Losers: (10 states, 12 districts): New York (2), Ohio (2), Illinois (1), Iowa (1), Louisiana (1), Massachusetts (1), Michigan (1), Missouri (1), New Jersey (1), Pennsylvania (1)

If a reapportionment were performed using projections of the 2010 state populations (mid-term trend model)

• Gainers (9 states, 14 districts): Texas (4), Arizona (2), Florida (2), Georgia (1), Nevada (1), North Carolina (1), Oregon (1), South Carolina (1), Utah (1)

• Losers (12 states, 14 districts): New York (2), Ohio (2), California (1), Illinois (1), Iowa (1), Louisiana (1), Massachusetts (1), Michigan (1), Minnesota (1), Missouri (1), New Jersey (1), Pennsylvania (1)

If a reapportionment were performed using projections of the 2010 state populations (short-term trend model)

• Gainers (9 states, 13 districts): Texas (4), Arizona (2), Florida (1), Georgia (1), Nevada (1), North Carolina (1), Oregon (1), South Carolina (1), Utah (1)

• Losers (11 states, 13 districts): New York (2), Ohio (2), Illinois (1), Iowa (1), Louisiana (1), Massachusetts (1), Michigan (1), Minnesota (1), Missouri (1), New Jersey (1), Pennsylvania (1)