Arizona Supreme Court says voters will decide on open primaries measure to overhaul elections

• After Maricopa County Superior Court Judge Frank Moskowitz ruled in favor of the measure on the eve of the August ballot printing deadline, the high court took the unusual step of sending the case back for further review.
• It's too late to remove Prop. 140 from the ballot, but the court could have ordered that votes for it not be counted.
• The Supreme Court found that Moskowitz improperly refused to consider evidence of tens of thousands of duplicate signatures. Moskowitz again rejected the challenge last month.

Why it matters: Prop. 140, also known as the Make Elections Fair Act, would dramatically change the way Arizonans elect partisan offices.

How it works: All candidates, regardless of party affiliation, would compete in a single primary election that's open to all voters. Between two and five candidates, no matter their party, would advance to the general election for each office, with the Legislature deciding how many.

• If more than two candidates advance to the general, the eventual winner would be elected through a form of ranked-choice voting (RCV).
• Under RCV, voters list candidates by preference, and if no one gets a majority, the candidate with the fewest votes is eliminated and their second-choice votes are given to the remaining candidates until someone has over 50%.
• If the Legislature fails to make a decision on the number of candidates, the secretary of state would decide.

Meanwhile, lawmakers last year referred a competing measure to the ballot.

• Prop. 133 would enshrine partisan primaries in the Arizona Constitution.
• If both measures pass, the one with the most votes would prevail.

What they're saying: Chuck Coughlin, who heads the campaign for Prop. 140, told Axios he looks forward to a campaign to "free Arizonans from the constraints of partisan primary elections."

• Proponents argue open primaries will create more competitive elections and give voters more choices, including in districts where one party currently dominates.

The other side: Scot Mussi, head of the Arizona Free Enterprise Club, which challenged the measure in court, said he was disappointed by the ruling.

• He noted in a press statement that a court-appointed special master concluded that 99% of the challenged signatures were duplicates, which would have left Prop. 140 without enough to qualify for the ballot.
• Moskowitz rejected the method used to determine duplicate signatures as unconstitutional.
• "Our organization proved that the special interest groups attempting to hijack Arizona's elections systems lacked the minimum number to qualify for the ballot to even be considered by voters in November," Mussi said.

Zoom in: Coughlin said Make Elections Fair AZ, the committee supporting Prop. 140, began a $1.3 million television advertising campaign on Monday, and said he expects to get $2.5 million soon from Unite America, an advocacy group that supports open primaries.