By Lawrence Hurley
WASHINGTON (Reuters) - The growing influence of Hispanic voters in the United States could be blunted by a case coming before the U.S. Supreme Court on Tuesday in which two voters backed by a conservative group are challenging the way Texas draws electoral districts.
At issue is whether these districts should contain the same number of people or whether they instead should contain the same number of eligible voters. The distinction may seem mundane, but the court's ruling in the case could be consequential.
Hispanic advocates and civil rights groups said a ruling backing plaintiffs Sue Evenwel and Edward Pfenninger could trigger nationwide political upheaval by diminishing the influence of Hispanic voters, who tend to back Democrats, and boosting the power of rural white voters, who tend to back Republicans.
Counting everyone and not just eligible voters magnifies the electoral influence of locales, typically urban, with sizable populations of people not eligible to vote, including legal and illegal immigrants as well as children.
Evenwel and Pfenninger maintain that the Texas process, based not on eligible voters but on total population, violated the long-established legal principle of "one person, one vote" endorsed by the Supreme Court in the 1960s.
The challengers said the state Senate redistricting map signed into law in 2013 did not equally distribute voters, improperly inflating the voting power of urban areas.
Among the people living in the urban districts are large populations of mainly Hispanic non-citizens and their children.
A broad win for the plaintiffs would be a "game-changer," according to Ilya Shapiro, a lawyer at the Cato Institute, a libertarian think tank that filed a brief backing the challengers.
The case, Shapiro said, is about "maintaining voter equality in the face of demographic developments that were unforeseen by the Supreme Court when it first decreed the one-person, one-vote principle."
Such a ruling would raise questions about the process used in every state and could especially impact those with large numbers of non-citizen immigrant populations such as California and Arizona.
A decision along those lines would "decrease representation for the Latino community," said Thomas Saenz, president of the Mexican American Legal Defense and Education Fund, which submitted a brief supporting the Texas redistricting plan.
The plaintiffs were recruited by the Project on Fair Representation, a conservative group that also brought a case challenging the use of racial preferences in university admissions that the Supreme Court will hear on Wednesday.
The dispute does not involve U.S. congressional districts. Under the Constitution, seats in the U.S. House of Representatives are distributed based on total state population.
(Reporting by Lawrence Hurley; Editing by Will Dunham)