In late September, the Heartland Institute, a libertarian think tank that receives donations from fossil-fuel companies, published a blog post titled “California Billionaire’s Renewable Energy Initiative Makes Arizona Ballot.” The billionaire in question was Tom Steyer, whose year-long effort to pass Proposition 127, an amendment to Arizona’s constitution that would require power companies to generate fifty per cent of their electricity from renewable sources by 2030, has faced aggressive opposition from the state’s largest utility, Arizona Public Service, or A.P.S. The blog post lamented a failed lawsuit filed by Arizonans for Affordable Energy, a political-action committee funded by A.P.S.’s parent company, to keep Prop 127 off the ballot, and quoted several opponents who believed the measure, now up for a vote in November, would be a costly mistake. “Prop 127 would tie Arizona’s future to technologies that do not deliver baseload electricity,” Mark Finchem, a Republican state representative, said, “and are arguably worse for the environment as a whole than the dependable technologies we already have.” The photograph accompanying the post depicted a wind-turbine farm, and, in the foreground, a dead bald eagle.

Arizona is the sunniest state in the country, with more than three hundred bluebird days per year. It is also projected to endure an additional month of hundred-degree days in the coming decades owing to climate change. Yet, despite the rapid decline in the cost of solar-energy technology and battery storage—to the point that, as an A.P.S. director told me, it now frequently outbids fossil fuels, even natural gas—in 2017, Arizona generated only six per cent of its electricity from solar, according to the ballot initiative’s advocates. The state currently requires utilities to generate eight per cent of their power from sources like solar and wind, scaling up to fifteen per cent by 2025. Natural gas, the largest source of Arizona’s net electricity generation, is imported from out of state. “Our most abundant resource in Arizona is our sunshine,” D. J. Quinlan, a spokesman for Clean Energy for a Healthy Arizona, the Phoenix-based political-action committee that Steyer is funding, said. “We need a nationwide transition to renewables. One of the first places we should be doing it is where it’s most efficient and cost-effective, and that’s here.”

Renewable-energy portfolio standards—known as R.P.S.s—rate among the country’s most powerful policy tools to slash greenhouse-gas emissions. One recent analysis found that between 2007 and 2013, renewable-power generation was responsible for nearly a third of reductions in U.S. energy-related carbon emissions. By 2025, the R.P.S.s that are currently in effect in twenty-nine states (plus Washington, D.C., Puerto Rico, the U.S. Virgin Islands, and the Northern Mariana Islands) will spur enough renewable-energy generation to power nearly fifty-six million homes a year. Establishing more ambitious R.P.S.s in every state, largely through measures like Prop 127, while accelerating the retirement of coal-fired power plants, could account for nearly six hundred and twenty million metric tons of avoided carbon emissions, or more than half of the amount needed to meet our commitments under the Paris Climate Agreement.

Last year, Steyer’s advocacy group, NextGen America, began campaigns for ambitious R.P.S. ballot initiatives in three states—Michigan, Nevada, and Arizona—that allow citizens to propose and vote on constitutional amendments. Michigan, Steyer said, seemed fertile ground in part because it is home to the Big Three automobile companies. “To the extent that they’re gonna be leaders in electric cars—which I think they all, at some level, want to be—this made sense,” Steyer told me recently at NextGen’s office in San Francisco. “You cannot plug an electric car into a coal-fired power plant and think that somehow you’re doing anything environmental.” Ultimately, two utilities in Michigan announced plans to impose a similar standard themselves. Nevada’s utilities have been relatively neutral on Steyer’s ballot initiative (known as Question Six) because they are fighting an even more ambitious measure that would eliminate electric-grid monopolies, and allow citizens to choose their energy provider.

In Arizona, however, where a recent poll found that three-fourths of the electorate wanted more solar energy, A.P.S. has spent close to twenty-two million dollars campaigning against Prop 127. “You’d think we were proposing something truly harmful and dangerous,” Steyer told me. He hasn’t been shy in returning the blows, spending nearly eighteen million dollars supporting Prop 127 through Clean Energy for a Healthy Arizona. Their biggest expense was a paid force of petitioners who spread out across the state to collect four hundred and eighty thousand signatures to get the initiative on the ballot, nearly twice the amount required by law. “We’re on the side of the angels,” Steyer said. “This is a black-hat, white-hat fight.”

Steyer and his coalition say that the problem is simple: A.P.S. is an investor-owned company, motivated primarily by its responsibility to protect profits for its shareholders, many of whom reside out of state. In 2017, the company made four hundred and eighty-eight million dollars, an increase of forty-six million from the previous year. The Arizona Corporation Commission (A.C.C.), a five-member elected “fourth branch” of state government, is supposed to keep the utility’s monopoly in check—setting limits on capital investments and pricing, while guaranteeing a certain margin of profit. But critics have long argued that the arrangement incentivizes utilities to “gold-plate,” or make inessential investments. (The phenomenon even has a name: the Averch-Johnson effect.) For A.P.S., a two-hundred-million-dollar gas-fuel plant would be more lucrative than a twenty-million-dollar solar array because the utility can charge higher rates to recoup its investment costs. Kris Mayes, a former Republican A.C.C. commissioner, who helped write the language of Prop 127, told me the Averch-Johnson effect explains why, in 2017, A.P.S. called for more than five thousand megawatts of new natural-gas additions, and almost no utility-scale renewables. “If they were truly acting in public interest,” Mayes said, “they would not be proposing fifty-four hundred megawatts of new natural-gas plants.”

Once Proposition 127 got on the ballot, Arizona’s attorney general, Mark Brnovich, had to sign off on its language. A.P.S. donated four hundred and twenty-five thousand dollars to Brnovich’s last campaign, and a hundred and fifty thousand dollars to the current effort to get him reëlected. (Steyer, through Clean Energy for a Healthy Arizona, has spent at least $3.6 million on an effort to unseat him this year.) In a move that the state’s elections director called “eyebrow-raising,” Brnovich added a clause to the ballot language—what voters will actually read before checking yes or no—saying that utilities must meet the new renewable-energy standard “irrespective of cost to consumers.” One of A.P.S.’s central claims—based on an economic analysis it funded, using data it provided—is that Proposition 127 would cause Arizonans’ annual utility bills to rise an average of a thousand dollars each year. But if that were the case, A.P.S., whose primary concern is shareholder value, should be all for it. “They are fighting this so hard because they know they will make more money off of natural gas than they will off of renewables,” Mayes said. “That’s my viewpoint as a former regulator.”

Within days, the “irrespective of cost” language was front and center in Arizonans for Affordable Energy’s television advertisements, which emphasized that any increase would be based on an initiative championed by a billionaire from California with larger political ambitions. (Steyer has hinted that he might run for President in 2020; he told me to call him on December 7th.) “You can’t go out and say everybody is the same across the U.S.,” Jeff Burke, the director of resource management at A.P.S., told me. “That’s what’s missing here, and that’s what the outside groups supporting the proposition don’t understand.”