The Supreme Court grappled Tuesday over whether states should change the way they redraw state and local legislative districts and whether requiring the change is practical. 

At oral arguments in a high-profile voting rights case, the justices explored the implications of the one-person, one-vote standard for drawing district boundaries. Almost all states now use total population to carve out legislative districts, but the challengers in the case told the justices a different metric should be used to give every voter an equal say in choosing representatives.

The attorney for two Texas voters who brought the case told the justices the state created districts with equal populations but with great disparity in the number of voters. That unconstitutionally dilutes the power of their votes, when compared to voters in districts with large numbers of non-voters, attorney William Consovoy said.

Texas has voter data but chooses to use total population in redistricting. Consovoy said the state doesn’t want to see the deviations it caused for one-person, one-vote. “All we’re asking the legislature to do is open its eyes,” he said.

Justice Anthony M. Kennedy, closely watched because he is often considered a swing vote, sought middle ground. He wondered why Texas isn’t required to avoid wide disparity in the number of voters in each district by drawing districts that are equal both in total population and in number of voters.

“Here it’s being completely — it’s being very substantially disregarded with this huge deviation,” Kennedy said to Scott Keller, the solicitor general of Texas who was defending the state’s plan. “Why can’t you use both?”

That would be “an onerous burden and change the nature of redistricting,” Keller replied. “States would inevitably have to disregard many other traditional redistricting factors, like compactness, continuity, keeping communities together …  And that would be the opposite of what the court has said that states have in this context, which is the leeway to structure their elections as part of the core function of their sovereignty.”

Kennedy replied, “That sounds highly probable to me.”

Principal Deputy Solicitor General Ian Gershengorn, arguing for the Obama administration, told the justices that data about voters is limited — and collection of such data is not constitutionally required, as is the census. The administration argued that states should be required to use total population.

“It would be very odd, we think, for the court to demand, as a constitutional standard, data that does not even have to be collected,” Gershengorn said.

A ruling that requires states to draw districts with an equal number of voters — or one that clarifies that states can choose whether to use voters or total population — could upend state legislative redistricting practices across the nation.

Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr. voiced opinions on one-person, one-vote more than 20 years ago, taking opposite positions.

Roberts, as an attorney in the solicitor general’s office in 1990, signed a Supreme Court brief opposing a challenge to the one-person, one-vote standard. The petitioners in that case sought what the Roberts brief called “a curious result.”

Alito, in a 1985 application to work for the Justice Department, said his decision to pursue a legal career came in part from concern about a series of Supreme Court decisions in the 1960s establishing the one-person, one-vote standard. Senate Democrats later threatened to filibuster his nomination to the court over his view.

Alito was an active questioner during the arguments, with questions indicating he thought states should have to consider equalizing voters to some degree. Roberts did not bring up his old argument, but Justice Elena Kagan asked a question that mirrored its language.

The Supreme Court will issue a decision in the case, Evenwel v. Abbott, before the end of the term in June.