EPA Administrator Michael Regan’s official rolled out the rule on Wednesday at a Washington event attended by carmakers, environmentalists and other groups.

President Joe Biden said the rule fulfills his promise to cut the nation’s carbon pollution in half by the end of the decade while promoting American workers. “Together, we’ve made historic progress. Hundreds of new expanded factories across the country. Hundreds of billions in private investment and thousands of good-paying union jobs,” Biden said in a statement.

“And we’ll meet my goal for 2030 and race forward in the years ahead.”

The regulation offers a test of Biden’s ability to drive an ambitious climate agenda while balancing the demands of key voting blocs, including young climate activists impatient for a swift turn away from gasoline-powered vehicles and unionized auto workers anxious about what the transition means for their jobs.

Former President Donald Trump has repeatedly vowed to repeal Biden’s policies — denouncing the electric vehicle push as “lunacy” and warning it would devastate automakers in the must-win swing state of Michigan.

The rule faces intense political opposition, and it will likely be challenged in court.

Indeed, the American Petroleum Institute and American Fuel & Petrochemical Manufacturers panned the rule Wednesday, saying it would eliminate most new gasoline-fueled cars in less than a decade “at a time when Americans are struggling with high costs and inflation.”

“This regulation will make new gas-powered vehicles unavailable or prohibitively expensive for most Americans. For them, this wildly unpopular policy is going to feel and function like a ban,” the groups said in a joint statement.

They also called on Congress to overturn the regulation through the Congressional Review Act, saying lawmakers must “make a decision whether to protect consumer choice, U.S. manufacturing workers and our hard-won energy security by overturning this deeply flawed regulation” and if they don’t, that they are “prepared to challenge it in court.”

Republicans seeking to overturn the rule are already sharpening their strategy. Sens. Pete Ricketts of Nebraska and Dan Sullivan of Alaska said Wednesday that they plan to introduce legislation to overturn the regulation.

“This rule is delusional. This is the Biden administration’s attempt to get rid of the internal-combustion engine without congressional authority,” the senators said in a joint statement. Sen. Shelley Moore Capito (R-W.Va.), the top Republican on the Senate Environment Committee, dinged the Biden administration for “deciding for Americans which kinds of cars they are allowed to buy, rent and drive” and said she appreciates Ricketts’ and Sullivan’s efforts to overturn the rule.

The rule sets carbon emissions limits for cars, light trucks and SUVs that would decline gradually beginning in model year 2027. It would also require carmakers to limit tailpipe pollution that contributes to smog and soot.

For all the rule’s aggressive goals, POLITICO and other outlets reported in February that the agency had relaxed the measure’s initial ramp-up in response to criticism from car companies and auto workers.

The final standards released Wednesday track most closely with the April 2023 draft rule’s so-called “Alternative 3.” It envisions a more gradual glide path toward the same end result as the original proposal — a projected 50 percent cut in vehicle carbon emissions by 2032.

Administration officials have stressed that the plan was designed to be technology-neutral, allowing car companies to build a variety of vehicles as long as they meet the standard.

“Different automakers are going to approach this in different ways,” a senior administration official, who declined to be named citing White House rules, told reporters. “You’ll have some automakers that maybe have a third of their fleet [made up of] plug-in hybrid electric vehicles.”

Environmental groups broadly approved of the regulation, despite the compromises. Transportation is the biggest source of climate pollution in the country, and passenger cars are the biggest contributor of those emissions.

“This is a day to celebrate American achievement,” Amanda Leland, executive director of the Environmental Defense Fund, said in a statement. “The step EPA is taking today will slash climate pollution and air pollution. It will bring more jobs for workers, more choices and more savings for consumers, and a healthier future for our children.”

Earthjustice, meanwhile, called on the U.S. auto industry to use the rule’s extra compliance time to speed up the transition to cleaner vehicles.

“It is critical that our large auto manufacturers take advantage of the extra time EPA has provided to ramp up their investments in clean, zero-emissions vehicles for the sake of our lungs, our health and the climate. The U.S. auto industry cannot afford to fall behind the rest of the world,” said Abigail Dillen, president of Earthjustice.

The auto industry has said it agrees with parts of the rule. But the Alliance for Automotive Innovation said “the future is electric,” and that automakers are “committed to the EV transition.”

“But pace matters,” said John Bozzella, president and CEO of the group, adding that modifying the timeline from an earlier version “was the right call.”

“These adjusted EV targets — still a stretch goal — should give the market and supply chains a chance to catch up. It buys some time for more public charging to come online, and the industrial incentives and policies of the Inflation Reduction Act to do their thing,” Bozzella said.

“And the big one? The rules are mindful of the importance of choice to drivers and preserves their ability to choose the vehicle that’s right for them,” he continued.