HOUSTON (AP) _ The number of Houston-area Hispanic voters has tripled since 1990, making it the region's fastest-growing voting group, according to a newspaper study.

But Hispanics have yet to harness their voting power, as Harris County has the largest Hispanic population in the United States that has never sent a Hispanic to Congress.

Hispanics make up nearly 40 percent of the county's population but just 15 percent of its electorate, officials said. Age and residency status are the biggest reasons. People younger than 18 and those who are not citizens cannot vote, categories that are thought to apply to 1 million Hispanics in Harris County.

Hispanics are expected to outnumber non-Hispanic whites in Texas by 2020. But the number of voting-age Hispanics are not expected to exceed non-Hispanic white voters until about 2050, the Houston Chronicle reported on its Web site Monday.

Some political experts compared Hispanic voters to a sleeping giant.

"The giant is waking up, and he's making a pot of coffee," Houston political consultant Marc Campos said.

Copyright 2008 The Associated Press.