Arizona's use of an independent commission for drawing state legislative boundaries survived another attack in a decision Wednesday by US Supreme Court.
In a unanimous vote, the justices said the commission did not violate the principle of one person, one vote when it drew a new map for the state's 30 legislative districts after the 2010 census.
A group of Republican voters said the new map created districts with a higher concentration of Republican voters, potentially diluting their voting power by packing them into a limited number of districts.
But Justice Stephen Breyer, writing for the court, said the variations in the population of the districts were well within the limits allowed by previous rulings that the principle of one person, one vote "does not demand mathematical perfection."
The court found that the variations were the result of efforts to abide by provisions requirements of the Voting Rights Act.
Gerry Hebert of the Campaign Legal Center, which lobbies for efforts to limit partisanship in redistricting, said the court "preserved the rights of minorities to elect candidates of their choice."
If Arizona had won, he said, it would have "disrupted thousands of other plans that have previously considered the Voting Rights Act in drawing their maps."
The Arizona plan survived a court challenge last year when the Supreme Court ruled that cutting legislatures out of the task of drawing district maps did not violate the US Constitution.