The proposition was sponsored by the liberal political action group NextGen America, founded by billionaire Democratic donor Tom Steyer.
The measure would have required Arizona utilities to achieve 50 percent of their electricity sales from renewable sources like solar and wind, but not nuclear, by 2030. That exceeded the current mandate imposed by the Arizona Corporation Commission, which requires utilities to get 15 percent of their power from renewables by 2025.
The latest returns from the Arizona Secretary of State's office on Wednesday morning show that more than 1,163,000 people voted "no," or 69.7 percent. The "yes" campaign on Prop 127 received 503,927 votes.
Massive amounts of money poured into Arizona during the battle over the measure, which was almost universally opposed by Republicans.
NextGen contributed over $22.5 million to a campaign committee, Clean Energy for a Healthy Arizona, to back the measure, according to campaign finance disclosures. Pinnacle West, the parent company of Arizona Public Service, donated $22.6 million to an opposition committee.
APS claimed that if the measure succeeded, it would force the closure of the Palo Verde Nuclear Generating Station west of Phoenix by disrupting Arizona's grid with intermittent power derived from solar energy.
Even before Prop 127 had officially made it onto the ballot, the Arizona Legislature took steps to de-fang the measure.
Prompted by APS lobbying, the Legislature passed a law that reduced penalties for utility companies that violated clean energy mandates imposed via the Arizona Constitution to no more than $5,000 and as little as $100.
Governor Doug Ducey signed HB 2005 into law in March, but the clean energy campaign maintained that the maneuver would not withstand a legal challenge.
Toward the end of the fight, as it became less and less likely that Prop 127 would succeed, the Clean Energy campaign turned its attention to Arizona Attorney General Mark Brnovich. The committee began running ads that tied him to APS based on campaign contributions, implying that Brnovich was a puppet of the utility company.
Brnovich, the campaign said, unfairly put his thumb on the scale by altering ballot language in Prop 127 that described the measure as taking effect “irrespective of cost to consumers.” The attorney general turned around and sued the Clean Energy committee for defamation over the ads.
In an interview on Monday, Clean Energy campaign spokesperson DJ Quinlan said that while the campaign’s strategy may have shifted, the campaign has made progress in pushing back on the utility company’s tactics.
But he denied that the Clean Energy committee shifted the goalposts from their original goal of boosting Arizona's renewable power.
“I think that while APS certainly is going to continue to spread money around in the political environment and isn’t going anywhere, I think what we’ve seen is a changing dynamic," Quinlan said.