A unanimous Supreme Court says an Arizona commission did not violate the principle of one-person, one-vote when it redrew the state's legislative districts in a way that created some with more residents than others.
The justices on Wednesday rejected a challenge from a group of Republican voters who claimed the state's Independent Redistricting Commission illegally packed GOP voters into some districts while leaving other Democratic-leaning districts with smaller populations.
A panel of federal judges upheld the new boundaries in 2014 after finding that the commission was trying to comply with a now-nullified provision of the Voting Rights Act.
State officials argued that slight differences in population were not enough to violate the Constitution's equal-protection clause.
Writing for the court, Justice Stephen Breyer said the one-person, one-vote principle "does not demand mathematical perfection."
The Supreme Court requires a state's legislative districts to have roughly equal numbers of people, but it has long said those numbers don't have to be exact. Differences of less than 10 percent are presumed constitutional unless challengers can show they are the result of discrimination or other invalid reasons.
In Arizona, the average population difference in redrawn districts was 2.2 percent, with a maximum difference of 8.8 percent. The plan placed more Republican voters in some districts that already were likely to elect GOP candidates and left other districts with smaller overall populations. Those districts have a greater concentration of Hispanic voters and are considered more likely to vote for Democrats.
Voters created the commission in 2000 to take on the politically charged job of drawing new maps every 10 years, instead of leaving it up to the Legislature.
In a separate case last year, the Supreme Court ruled that cutting lawmakers out of congressional redistricting is not unconstitutional even though state legislatures have the power to set the "times, places and manner" of holding congressional elections.