Scott Pruitt, administrator of the Environmental Protection Agency and second only to President Trump in the climate denial game, proposed on Monday revising — which definitely means relaxing and probably means crippling — the ambitious, groundbreaking greenhouse gas and fuel-economy standards approved during the Obama administration.

Though the devil will lie in the final details, the reversal puts Mr. Pruitt’s E.P.A. on a collision course with California, which can set its own emissions standards, thereby creating two car markets with different emissions standards. It would deprive consumers of billions of dollars in savings at the gas pump. It would do nothing to reduce imports of foreign crude oil. It would slow the steady technological advance toward cleaner cars.

And — no surprise here — it would continue Mr. Trump’s yearlong demolition of every important policy Barack Obama put in place to fight global warming. The Clean Power Plan to limit greenhouse gas emissions from power plants? Consigned to the dustbin. America’s participation in the historic Paris agreement on global warming? Withdrawn. John Kerry’s decision when he was secretary of state to block the Keystone XL oil pipeline from Canada? Revoked. And now on the chopping block, the 2012 auto efficiency rule aimed at curbing carbon emissions in the transportation sector, the country’s biggest source of planet-warming gases.

But here’s something interesting. The only conceivable beneficiaries of Mr. Pruitt’s scheme — the automakers, whose trade groups and lobbyists have been pressuring the White House for more lenient rules — may not be all that crazy about the plan, either. Bill Ford, the chairman of Ford Motor Company, and Jim Hackett, the company’s chief executive, wrote in a blog post last week that while they would like more “flexibility” on meeting the rule, “we support increasing clean car standards through 2025 and are not asking for a rollback.”