SEATTLE — A groundbreaking law that forces companies in Washington state to reduce their carbon emissions while raising billions of dollars for climate programs could be repealed by voters this fall, less than two years after it took effect.

The Climate Commitment Act, one of the most progressive climate policies ever passed by a state Legislature, is under fire from conservatives, who say it has ramped up energy and gas costs in Washington, which currently has the third-highest gas prices in the nation. The law aims to slash emissions to almost half of 1990 levels by the year 2030.

It requires businesses producing at least 25,000 metric tons (27,557 U.S. tons) of carbon dioxide, or the equivalent in other greenhouse gases including methane, to pay for the right to do so by buying “allowances.” One allowance equals 1 metric ton (1.1 U.S. tons) of greenhouse gas pollution and each year the number of allowances available for purchase drops, theoretically forcing companies to find ways to cut emissions.

Supporters of the policy say not only would a repeal not guarantee lower costs, but billions of dollars in state revenue for years to come are at stake. Many programs already are or will soon be funded by money from polluting companies, including projects on air quality, fish habitat, wildfire prevention and clean energy.

“The grand policy goal is the higher-level thing of fighting climate change, reducing carbon emission,” said Todd Donovan, a professor of political science at Western Washington University. “But you get down below 30,000 feet to the voters and it’s, ‘How does this effect my gas taxes?’”

The group behind the repeal effort, Let’s Go Washington, says the carbon pricing program has increased consumer gasoline costs by between 43 and 53 cents per gallon, citing the conservative think tank Washington Policy Center.

For months Let’s Go Washington, which is primarily bankrolled by hedge fund executive Brian Heywood, has held more than a dozen events at fuel stations to speak out against what it calls the “hidden gas tax.” Last month at a station in Vancouver, in southwestern Washington, the group lowered gas prices by $1 for two hours by subsidizing the difference to show what reduced prices would look like.

“It’s making everything more expensive, because everything you buy gets delivered to the store or to your door on a truck,” Let’s Go Washington spokesperson Hallie Balch said in a video about the initiative last month.

The average price at the pump for regular gas has gone as high as $5.13 per gallon since the auctions started in February 2023, though it has since fallen and stood at $4.05 this month, according to GasBuddy. The state’s historic high of $5.54 came several months before the auctions began.

Supporters of keeping carbon pricing have showcased the many programs it finances and could disappear if the repeal succeeds, including ones to help Native American tribes respond to climate change, for communities to build clean energy projects and for addressing air pollution.

Without the program, the Office of Financial Management estimates, $758 million would be lost in state revenue in the next fiscal year and $3.1 billion over the following four years. During this year’s legislative session, state lawmakers approved a budget through fiscal year 2025 with dozens of programs funded by carbon pricing revenue, with belated start dates and stipulations that would not take effect if that disappears.

Washington was the second state to launch this type of program, after California. It started out with aggressive emissions targets of 7% annual decreases, set to ease up from 2031 on. Repealing it would sink plans to link up Washington’s carbon market with others and could be a blow to its efforts to help other states launch similar programs.

A diverse coalition is behind the movement to keep carbon pricing, including most of the federally recognized tribes in Washington, some of its biggest tech giants, national environmental groups TV personality and science advocate Bill Nye of “Bill Nye the Science Guy” and even at least one fossil fuel company. BP America, which was approved to participate in the auctions, contributed more than $2 million to the campaign, saying it supported the measure when it was passed and wants it to stay intact.

The fuel giant’s support is likely due to the fact that keeping the policy in place would provide regulatory certainty that it can plan for, said Aseem Prakash, professor of political science and founding director of the University of Washington’s Center for Environmental Politics.

Supporters of the law have raised more than $16 million, far surpassing the $7 million that Let’s Go Washington has brought in to spend on this and six other initiatives.

The repeal side submitted more than 400,000 signatures to get Initiative 2117 on the November ballot.