WASHINGTON — Practical concerns about forcing states to abandon the way they have drawn electoral districts for more than 50 years seemed to give a key justice pause Tuesday in a Supreme Court case of immense importance to the nation's growing Latino population.
The court heard arguments in a case from Texas on the meaning of the principle of "one person, one vote," which the court has said requires that political districts be roughly equal in population.
But it has left open whether states must count all residents, or only eligible voters, in drawing district lines.
In Texas, and other states with large immigrant populations, the difference is more than academic. Urban districts include many more people who are too young, not citizens or otherwise ineligible to vote.
Two rural Texas voters are challenging the use of total population data in drawing state Senate districts because they say it inflates the voting power of city dwellers at their expense.
Their arguments seemed to make some headway Tuesday with Justice Anthony Kennedy, the pivotal vote on so many close high court cases.
When some districts of roughly equal population have dramatically different numbers of eligible voters, shouldn't Texas "at least give some consideration to this disparity that you have among voters?" Kennedy asked.
Later he wondered whether states could produce districts that were roughly equal in terms of overall population and eligible voters, saying, "Why is one option exclusive of the other? Why can't they have both?"
Texas Solicitor General Scott Keller said such an outcome could only be achieved at the expense of other traditional requirements about redistricting, including drawing relatively compact districts that don't split counties.
Kennedy sounded persuaded. "That sounds highly probable to me," he said.
The Texas case was one of three matters before the court on Tuesday that dealt with redistricting.
The justices also considered a challenge from Republicans over whether Arizona's state legislative districts were redrawn in a way that illegally shifted voters to give Democrats an advantage. The case also invokes the "one person, one vote" principle in asking whether slight differences in population that typically pass muster are nonetheless problematic if districts are drawn for partisan advantage or to comply with a now-defunct provision in the Voting Rights Act.
In yet a third case, the court unanimously revived a challenge by some Maryland residents to their state's 2011 redrawing of its congressional districts, ruling that their case must be heard by a panel of three judges, not a single judge.
The arguments in the Texas case were unusual in several respects. The justices displayed little of the aggressiveness that often marks Supreme Court arguments and Justice Antonin Scalia said nothing at all during the hourlong session.
Civil rights groups say forcing states to change their method would damage Latino political influence. Texas picked up four congressional seats after the 2010 census, mainly because of the growth in its Hispanic population.
Chief Justice John Roberts and Justice Samuel Alito appeared most open to the challengers' argument, but Scalia, another usually reliable conservative voice, did not comment at all.
"It is called ... one person, one vote. That seems to be designed to protect voters," Roberts said.
The court's liberal justices seemed more clearly disposed to upholding the districting plan for the Texas Senate that is being reviewed.
Questioning William Consovoy, the Texas voters' lawyer, Justice Ruth Bader Ginsburg noted that a decision in his favor would mean that women in America should have been ignored in redistricting decisions before they won the right to vote.
Ginsburg also pointed to a half-century tradition of states using total population. "Now you're saying they can't do it anymore," Ginsburg said.
Consovoy responded that if "tradition were the rule," the court's landmark "one person, one vote" cases would have come out the other way.
His clients, Texas residents Sue Evenwel and Edward Pfenninger, live in mainly rural districts outside Houston. Their districts have at least 170,000 more eligible voters than a downtown Houston district with equal population.
If the court upholds the Texas districts as drawn, it could say that the use of total population does not violate the Constitution. Or it could rule that states may choose which method to use.
Justice Department official Ian Gershengorn argued Tuesday that the once-a-decade census that produces the total population count is the only reliable population data.
Keller, representing Texas, urged the justices to allow states to choose.