The number of Hispanics in the United States rose by 1.4 million over a year’s time to 45.5 million as of last July, continuing rapid growth that could increase their influence.

This election year has focused more attention on how much it is increasing.

Nine of the top 10 states with the highest growth rates in their populations were in the South, according to new census data released Thursday.

South Carolina topped the list with an 8.7 percent increase, gaining 13,569 Hispanics, according to an analysis of the Census data by William Frey, a demographer at the Brookings Institution. The state’s total Hispanic population was 168,920 last July 1, a 76 percent increase from July 2000.

Other Southern states that saw increases are Tennessee, with 8.1 percent growth; North Carolina, 7.8 percent; Georgia, 7.1 percent; Alabama, Mississippi and Kentucky, 7 percent; Arkansas, 6.8; Louisiana, 6.5 percent. Florida had a 3.6 percent gain, which ranked 37th among states.

Michigan’s Hispanic population increased 23.2 percent, according to the analysis, from 326,955 to 402,797. Michigan’s population is now 4 percent Hispanic.

Utah ranked eighth with a 6.9 percent growth rate.

For the second consecutive year, Texas accounted for more of the gains in the numbers of Hispanics than California. Texas’ share was about 21.2 percent of the additional Hispanics in 2007, while California’s share was 18.5., according to Frey’s analysis. But California still leads in total number of Hispanics with 13.2 million, compared to Texas’ 8.6 million.

With those increases boosting Hispanics to 15.1 percent of the U.S. population, voting booths are being watched closely this year for Hispanic turnout.

Some Hispanic advocacy groups predict about 10 million Hispanics will show up at the polls, motivated by the usual concerns about the economy, health care and the war and an added catalyst of dismay over attitudes from anti-immigration movements.

“We obviously know that Latino population growth is not perfectly mirrored in the Latino voting population,” said Clarissa Martinez, National Council of La Raza director of immigration and national campaigns.

Hispanics are a significant part of the electorate in the battleground states of Nevada, New Mexico, Florida and Colorado, she said. “Look at the primary turnout, Latinos are demonstrating they are engaged in numbers we haven’t seen before.”

In California’s March Democratic primary, Hispanics accounted for 31 percent of the vote, up from 16 percent in 2004, according to exit polls. In Texas, their share of the Democratic primary vote rose from 24 percent to 32 percent.

In some states, the change is smaller. In Ohio, their turnout was up to 4 percent in the Democratic primary, compared with 3 percent in 2004.

Along with low turnout at elections, Hispanics are underrepresented among those elected.

There were 5,129 Hispanic elected officials in local, state and federal office as January 2007, about 1 percent of all office holders, said William Ramos, Washington director of the National Association of Latino Elected and Appointed Officials. There were 5,132 in January 2006.

Expectations are that growth of the Hispanic population in the Southeastern U.S. will help raise those numbers, Ramos said.

Larry Gonzalez, a lobbyist with the Raben Group, says he experiences the growing influence of the increasing Hispanic population when prospective clients come to his lobbying firm looking for ways to reach the community.

“It’s clear to us there’s a whole economic impact from the growth of the Latino community, said Gonzalez, who formed the Hispanic Lobbying Association. “That’s what we see on the lobbying end, when people come to us and say, ’Help us engage the (Hispanic) community.”’

Gonzalez said the latest numbers should underscore the need for policymakers and politicians to pay attention to the Hispanic population.

“It bears repeating, the future of Americans is going to depend on the future of the success of Latinos,” he said.

Congress gave that population’s growth a limited nod Tuesday night when it passed legislation to create a commission to study whether to add a museum in the Smithsonian Institution system dedicated to the contributions of U.S. Hispanics. Money still must be provided for the commission.

On the Net: U.S. Census Bureau: http://www.census.gov