Power shift: how the results of the 2010 Census are changing the political map--and the balance of power in Washington.

• Author: Smith, Patricia
• Position: NATIONAL

Remember all the talk last spring about how important it was to fill out those Census forms that came in the mail?

Now everyone can see why, as the nation's political map is literally being redrawn as a result of the data that the Census collected: 18 states are gaining or losing seats in the House of Representatives next year. The seats are moving primarily from states in the slow-growing Northeast and Midwest to the faster-growing South and West.

The U.S. population increased 9.7 percent over the last decade to a total of almost 309 million. But since the number of seats in the House stays the same at 435, some of those seats need to be redistributed among the states so that all congressional districts have roughly the same number of voters. (The Senate isn't affected by the Census, since every state, no matter how big or small, gets two seats.)

Texas, whose population increased by more than 20 percent, is the biggest winner, gaining four House seats (see map). Ohio, on the other hand, whose population grew by just 1.6 percent, will lose two seats. Louisiana, whose population shrank in the aftermath of Hurricane Katrina in 2005, is the only southern state losing a seat.

New York will lose two House seats, down to 27. (The last time New York had 27 House seats was in the early 1820s.) This continues a slide that began after World War II, when New York's congressional delegation peaked at 45 members.

The Constitution mandates the national headcount every 10 years, and the tally reveals not only America's changing demographics--in terms of race, gender, age, and other categories--but also its shifting population. And that affects political representation in Washington--and how billions of federal dollars are distributed to the states.

Electoral College

Shifting power in Congress also means shifting clout in presidential elections. Each state's Electoral College votes are equal to its number of seats in the House, plus two for its Senators. (Oregon, for example, with 5 Congressmen and 2 Senators, has 7 electoral votes.)

The new congressional map will take effect next year and could impact the presidential race, with Republican-leaning states in the South and West gaining electoral votes at the expense of Democratic-leaning states in the Northeast and Midwest: If President Obama were to win the same states he carded in 2008, he would end up with six fewer electoral votes.

That said, the population gains in the South and West were driven...