WASHINGTON — U.S. racial minorities accounted for roughly 85 percent of the nation’s population growth over the last decade — one of the largest shares ever — with Hispanics accounting for much of the gain in many of the states picking up new House seats.

Preliminary census

estimates also suggest the number of multiracial Americans jumped roughly 20 percent since 2000, to over 5 million.

The findings, based on fresh government survey data, offer a glimpse into 2010 census results that are being released on a state-by-state basis beginning this week. New Jersey, Mississippi, Virginia and Louisiana are the first to receive the census redistricting data, which will be used in the often contentious process of redrawing political districts based on population and racial makeup.

“There are going to be a lot of additional Hispanic officials elected when redistricting is done,” said E. Mark Braden, a former chief counsel to the Republican National Committee who now advises state governments on redistricting. “But folks in power don’t give up control that easily — there will be tension between the ins and outs.”

Arkansas, Indiana, Iowa and Maryland are among the states scheduled to receive their data next week. By law, all states must receive their redistricting data by April 1.

Four of the eight states gaining House seats owe roughly half or more of their population gains over the last decade to Hispanics. They include Texas, which picks up four seats; Florida, which will add two seats; and Arizona and Nevada, picking up one seat apiece.

In Georgia and Washington state, which also gain one seat each, Hispanics combined with other minority groups accounted for a majority of their growth since 2000.

Among states losing House seats, Louisiana and New Jersey each would have posted a net population loss, and Michigan would have sustained bigger declines, if it hadn’t been for Hispanic growth. Latinos also made up roughly 60 percent or more of the growth in New York, Pennsylvania, Ohio, Illinois, Iowa and Massachusetts — which each lose a seat — raising questions as to whether remaining districts in those states will need to accommodate emerging Hispanic voting blocs.

Broken down by voting age, minorities accounted for roughly 70 percent of U.S. growth in the 18-and-older population since 2000, and Hispanics made up about 40 percent. Hispanics also represented more than half the growth share of the voting-age population in Texas and California.

“The growth of the Hispanic community is one of the stories that will be written from the 2010 census,” Census director Robert Groves said Wednesday, previewing major demographic trends, including the movement of many minorities from city to suburb. “We should see a big difference from 2000 to 2010.”

Thomas Saenz, president and general counsel of the Mexican American Legal Defense and Education Fund, which successfully challenged the redrawing of a majority Hispanic Texas district that weakened the Latino vote after the 2000 census, said his group was expecting to see “a minimum of nine additional Latino-majority House seats” based on 2010 results, if states comply with federal law.

The 1965 Voting Rights Act protects the interests of substantial minority voting blocs, in some cases requiring states to get federal approval of state redistricting plans. The law does not ensure that minorities are elected to office, but that votes of minorities are not overly weakened in a way that keeps them from electing the candidates they prefer. Based on population growth, MALDEF has suggested that several new Hispanic districts are warranted in places such as Texas, Florida, California and New York.

“We’ll be monitoring everywhere,” Saenz said.

Jeffrey M. Wice, a Democratic redistricting attorney, said states also will have to decide whether to consider citizenship when drawing political lines. Many lower federal courts have ruled that citizenship data should be used if available to determine whether a minority voting bloc has been unduly weakened — an issue that could mix already intense redistricting fights with contentious immigration politics.

Some demographers say the available census data on citizenship rates may not be reliable in certain situations because the numbers are five-year averages from 2005-09.

“This is a new area, and the Supreme Court has largely been silent on the issue,” Wice said. “In some places, the use of citizenship data may dilute the ability of Hispanic communities to be fairly redistricted. Republicans may attempt to base redistricting on citizenship data in New Jersey, so that is one state to keep an eye on.”

The preliminary demographic numbers are based on the Census Bureau’s Current Population Survey as of March 2010, as well as comparisons of the 2000 census with 2009 demographic estimates and the 2009 American Community Survey, which samples 3 million U.S. households. According to those figures, minorities represented between 81 percent and 89 percent of the U.S. population growth since 2000, higher than the official 80 percent share in 2000.

The minority growth share in 2010 is the largest in recent memory, with only the influx of European minority immigrants such as Italians, Poles and Jews in the late 1800s possibly rivaling it in scope, said William H. Frey, a demographer at Brookings Institution who analyzed the census data.

Other findings:

—In all, non-Hispanic whites make up roughly 65 percent of the U.S. population, down from 69 percent in 2000. Hispanics had a 16 percent share, compared with 13 percent a decade ago. Blacks represent about 12 percent and Asians roughly 5 percent. Multiracial Americans and other groups made up the remaining 2 percent.

—California, Texas, New York and Hawaii were among the states with the largest number of people who identified themselves as multiracial.

—Some 40 states show population losses of white children since 2000 due to declining birth rates. Minorities represented all of the increases in the under-18 population in Texas and Florida, and most of the gains in the child population in Nevada and Arizona.

“The new engines of growth in America’s population are Hispanics, Asians and other minorities,” Frey said. “But it’s just the tip of the iceberg. For the under-18 population — potential voters in the not-too-distant future — minorities accounted for virtually all the growth in most U.S. states.”

“Political strategists and advocates, especially in growing states, cannot afford to ignore this surging political wave,” he said.

In December, the Census Bureau officially reported the nation’s population was 308,745,538, up from 281.4 million a decade ago. The growth rate for the past decade was 9.7 percent, the lowest since the Great Depression, with most of the growth occurring in the South and West.

The population changes will result in a shift of House seats taking effect in 2013.