The La Paloma complaint builds on that argument. It contends that subsidies and mandates for solar and wind power — including rebates for residential solar-panel programs and requirements that growing percentages of utility-scale systems come from carbon-free sources — have left California dependent on energy sources that are unreliable for round-the-clock power.

Critics say Mr. Beal wants the commission to create a subsidy for fossil-fuel plants, paid for by utility customers in their rates, and effectively remove the cost advantage that renewable-energy plants now have. Fossil-fuel plants are better able to ensure a continuous supply of electricity because storage capacity is not yet sufficient to keep solar or wind energy flowing when the sun isn’t shining or the wind abates. And one of the commission’s primary responsibilities is to ensure the reliability of the grid.

Opposition to the Beal effort has poured in from energy markets in the Eastern and Northeastern United States, California regulators, the state attorney general, environmentalists and consumer groups. They are troubled by the potential impact of a decision siding with Mr. Beal and the possibility that regulators could apply it nationwide.

Despite his low profile, there is little question of Mr. Beal’s political leanings. He created a pro-Trump super PAC, Save America From Its Government, which published a 2016 newspaper advertisement that was headlined “Obamacare: A Crash Course in Government Inefficiency” and asked, “Is America a communist country?” During the presidential campaign that year, Mr. Trump listed him as one of his economic advisers.

And in a postelection interview with The Dallas Morning News, while describing himself as “a Democrat on virtually all social issues,” Mr. Beal said Mr. Trump’s victory was “the first time in my lifetime where a step in the right direction has been taken to reduce the government and get it out of people’s lives.”

“That’s all we need to thrive,” he said.

But Tyson Slocum, director of the energy program at the nonprofit consumer-advocacy organization Public Citizen, said he had not seen evidence of Mr. Beal’s pursuing an ideological agenda in the La Paloma case so much as a financial one.