Following each decennial census, the House of Representative’s districts are redrawn to make them roughly equal in population – although each state gets at least one seat regardless of the population. The House now comprises 435 districts. Not surprisingly, redrawing districts usually triggers contentious partisan wrangling if new lines help or hurt either party.

This time the census will affect the number of districts in 18 states and the results will be in time for the next election of president and Congress in 2012. This may have some sobering implications for an Obama re-election campaign because each state’s electoral vote is equal to the number of congressional seats it has, plus two more for its senators.

The Census Bureau announced Tuesday that as at 1 April 2010, America’s population had reached 308,745,538, up some 9.7% from its total of 281.4 million in 2000. While this is a significant growth – in contrast to most European nations or Japan – the rate of increase was still the lowest since the Great Depression. France and England each grew about 5% in the past decade, Japan was largely unchanged, and Germany’s population is actually declined. China, meanwhile, grew aboput 6% and Canada’s growth rate was slightly bigger than that of the US.

At the state level, Michigan was the only state to actually lose population in the past decade. Nevada, with its 35% increase, grew the fastest in the nation. Based on population numbers, Texas gained four new House seats, Florida two and Arizona, Georgia, Nevada, South Carolina, Utah and Washington gained one new congressional district each. Meanwhile, Ohio and New York lose two seats each, and Illinois, Iowa, Louisiana, Massachusetts, Michigan, Missouri, New Jersey and Pennsylvania lose one each.

This means that in the next election, Florida will have as many House of Representatives members as New York at 27. California will continue with 53 and Texas will rise to 36. Importantly, in the 2008 election, Barack Obama lost in Texas and most of the other states which have gained, while he carried most of the states that are scheduled to lose seats, including big states like Ohio and New York. The average population of a new US House of Representatives district will be 710,767.

While the constitution determines that congressional districts (and electoral votes) should conform to population size, the constitution is silent on how each state is divided into districts – or who will actually carry out this process. Over time this has led to all manner of creatively designed electoral districts – including one particularly emblematic district in Massachusetts in the early 19th century that looked astonishingly like a writhing salamander imposed on the state map. That “redistricting” process, spearheaded by then-governor Elbridge Gerry, led to a ubiquitous bit of political nomenclature – “gerrymandering” – or the drawing of improbably shaped electoral districts designed to maximise partisan support in a particular district for electoral gain.

This census has also pointed to the fact that while the country as a whole grew in population, this is the first decade since 1850 that California did not gain at least one congressional seat and additional electoral votes. Although the Golden State’s population still grew, this time it only gained at around the same rate as the country as a whole, in contrast to those states that gained share in the national population total. For California, this represents a startling comeuppance and is a statistical measure of the end of its automatic pole position as ground zero for the nation’s political and societal future.

Of larger significance for American politics is that this census highlights a decades-long shift of population away from the Northeast and Midwest towards the South and Southwest. Population, and thus presidential electoral votes and congressional districts, have been migrating away for years from generally Democratic states such as New Jersey, Michigan and Massachusetts towards typically Republican ones like Texas and contested battleground ones like Florida.

Overall, in the past 70 years, 79 seats have shifted to the South and West from the Northeast and Midwest. The US is still growing quicker than other developed nations. The South had the fastest growth since 2000 at 14.3%, while the West was close behind at 13.8%. By contrast, the Northeast had 3.2% and the Midwest just a hair below 4%.

The declining US growth rate since 2000 can be explained in part to a reaction to the economic meltdown of 2008. That event drove both US births and illegal immigration to a near standstill compared with previous years. The 2010 census measures the number of people actually resident in the country – citizens as well as legal and illegal immigrants – but not Americans normally domiciled outside the country.

Beginning early in 2011, most state governments will use sophisticated computer-generated data on voting patterns to slide specific neighbourhoods in or out of their newly redrawn House districts, thereby tilting them more towards Democratic or Republican pluralities – more subtly than Elbridge Gerry’s cronies could ever do. While politicians may sometimes choose to play it safe, doing a backroom deal to protect Republican and Democratic incumbent congressmen alike, at other times the party in control at state level will try to reconfigure a state’s electoral map to dump as many opponents as possible.

State governments’ ability to gerrymander districts has been somewhat limited by court rulings that require roughly equal populations and the 1965 Voting Rights Act that protects ethnic minorities in those states subject to continuing US justice department oversight. Crucially, last month’s elections put Republicans in full control of a majority of state governments, giving the GOP an overall edge in the “redistricting” process, despite these protections.

For Obama, his electoral burden for a 2012 re-election campaign will be the need to hold onto all his previously won states – including Republican-trending battleground states like North Carolina, Virginia and Florida – and then somehow find a way to win yet another state that has six to eight electoral votes. Not an easy task.

Even worse for Democrats is the results of this census will also subtract previously safe Democratic-held seats from some state delegations and that, in turn, will create an equivalent number of corresponding new and very likely Republican-leaning congressional districts in states like Texas, Florida, Arizona, Georgia and Utah for the 2012 election.

As Clark Benson, a political consultant with Polidata, said, “Especially because of the 2010 election, Republicans are in a better place than they have been in decades.” But maybe there is a bit of light for Democrats as well. Much of the actual growth in the South and Southwest is attributable to the rapid growth in Hispanic Americans who tend to vote Democrat. That means that, while Texas is getting four new seats, it is not clear they will be Republican ones. Depending on how this ultimately plays out, Texas might even tip towards Democrat in specific congressional districts, although it is unlikely to be in play at the presidential election level.

Regardless of who and which party wins, according to the trend-spotting American politics blog, “Politico”, the impending “redistricting” of congressional seats in states that will now lose seats marks: “The beginning of a season of politics in its rawest form, a time of ruthlessness, scheming and, above all, self-preservation. For the next year, ambitious and sharp-elbowed legislators around the nation will look to Machiavelli, rather than Jefferson or Hamilton, for inspiration as they draw the congressional maps that will begin and end political careers and determine the partisan makeup of Congress during the next decade.

“Some incoming House freshmen are already marked men and women ? before they’ve been sworn into office. Some veterans are about to be brusquely pushed into retirement. A few members of Congress will be forced into head-to-head battles with colleagues in order to survive another term. All in all, it’s a harrowing exercise in political Darwinism.”

These struggles will have the sharpest elbows in the states of Illinois, Iowa, Louisiana, Massachusetts, Michigan, Missouri, New Jersey, New York, Ohio and Pennsylvania – all places that will lose seats as a result of population shifts over the past decade.

The 2010 American head-count will almost certainly turn into real political head knocking in the coming two years, bringing an another variable in the race to the power. Never boring, US politics. DM

For more, read Politico, AP, The Washington Post, The New York Times and Wikipedia. For the primary source material, go to the 2010 Census site itself.

Photo: Director of U.S. Census Bureau Robert Groves talks to the media after a presentation of the 2010 Census U.S. population at the National Press Club in Washington December 21, 2010. Data from the U.S. Census Bureau released Tuesday showed that the country’s population has risen 9.7 percent in the past decade to stand at 308.7 million. REUTERS/Yuri Gripas.