2010 Census Moves 12 House Districts

December 21, 2010— -- Census data released Tuesday led to a seismic shift in the allocation of Congressional seats, with Republican-leaning Sun Belt states gaining seats and Democratic-leaning Rust Belt states losing.

Every 10 years, after the census gauges population shifts, government officials divvy up the nation's 435 seats in Congress. This year's census data resulted in a shift of 12 seats across 18 different states.

As demographic and redistricting experts predicted, Texas was the big winner, picking up four new House seats and capping seven consecutive decades of gains. The state now has a total of 36 seats.

Florida was second with two more seats, with the smaller Sun Belt states of Georgia, South Carolina, Arizona, Utah and Nevada picking up one each, and northwest Washington grabbing one as well. All but one of the gaining states have a Republican governor, implying long-term damage to Democrats for future elections.

State legislatures will redraw boundaries for congressional districts next year. The process is called redistricting or "gerrymandering," after a salamander-shaped district created by Gov. Elbridge Gerry of Massachusetts in 1812. It is a bitter political process with high stakes for both parties.

The biggest losers were in the Northeast and Midwest, with New York and Ohio losing two seats each. Illinois, Iowa, Louisiana, Massachusetts, Michigan, Missouri, New Jersey and Pennsylvania each lost one.

Boiling it down to red states gaining over blue states is overly simplistic, according to demographers.

"As they grow, the people who enter those states are coming from other states, they bring with them the cultures and the belief systems that they had in other states as well," Census Bureau director Robert Groves told ABC News. So those Sun Belt states are not just growing in size, they are also shifting in character.

The congressional gains also mean a change in Electoral College votes. If the 2008 Presidential election had been held with the newly reapportioned Congress, President Obama would have gotten six fewer electoral votes; the growth was primarily in states that favored his opponent, John McCain.

"On its face, 6 seats isn't much of a dent. But, it also assumes that Obama wins some of these fast growing swing states – like Florida and Nevada – again in 2012," said Amy Walter, ABC's Political Director.

"In order to chip away at Obama's 2008 electoral college advantage, the Republican nominee will still need to be able to pick up states all across the country - including the Midwest and West," Walter added.