By Lawrence Hurley
WASHINGTON (Reuters) - The Supreme Court on Wednesday unanimously upheld the state legislative districts in Arizona drawn by an independent commission, rebuffing complaints that the electoral maps diminished the clout of Republican voters.
The court, in its 8-0 ruling, said the commission that draws legislative boundaries did not violate the U.S. Constitution's principle of "one person, one vote."
The case focused on state legislative districts drawn for the 2012 election based on 2010 census numbers. The challengers said the new districts favored Democrats over Republicans by packing Republican voters into certain districts in a way that would minimize their influence in neighboring districts while enhancing the sway of Democratic voters.
In mapping out the state legislative districts, Arizona's independent commission carries out a function that in most other states is handled by state legislators.
Writing for the court, liberal Justice Stephen Breyer said the deviations in numbers between district populations was not significant enough to be legally troubling, particularly as the state's redistricting commission was trying to comply with the federal Voting Rights Act, which protects minority voters.
The challengers "have not shown that it is more probable than not that illegitimate considerations were the predominant motivation behind the plan's deviations from mathematically equal district populations," Breyer wrote.
A federal court in Arizona upheld the districts in a 2014 ruling, saying the commission had made a "good faith attempt" to comply with the Voting Rights Act. The group of Republican voters who brought the case then appealed the matter to the U.S. Supreme Court.
The case was the second in as many years concerning Arizona's independent commission. In June 2015, the court rejected another challenge to the commission's role in drawing congressional districts.
In that decision, the court found that the ballot initiative that set up the commission did not violate the U.S. Constitution's requirement that state legislatures set U.S. House of Representatives district boundaries.
Wednesday's ruling was the second by the court this month touching upon the issue of "one person, one vote."
On April 4, the justices also ruled unanimously in a Texas case to uphold the method all 50 states use in drawing legislative districts by counting every resident and not just eligible voters. In that case, the justices rejected a conservative challenge that could have diminished the influence of urban Hispanics.
The case is Harris v. Arizona Independent Redistricting Commission, U.S. Supreme Court, No. 14-232.
(Reporting by Lawrence Hurley; Editing by Will Dunham)