Some of the most glaring errors described in this article were detected by EPA staff before the proposal’s publication. Others were affirmed in recent public comments from Honda, a major automaker. The Atlantic also confirmed some alleged errors with economists who were not involved in their discovery, who described them as “incontrovertible.”

Taken together, the errors artificially lower the rollback’s costs and boost its safety benefits, experts say. Every single error so far identified appears to tilt the analysis in Trump’s favor.

“There’s a systematic bias in all of these to inflate the crash fatalities [under the Obama-era rules]. We have not yet found any mistakes that work in the other direction,” says Kenneth Gillingham, an economics professor at Yale and a former senior economist in the Obama administration.

“Usually, in any rule-making, you can look and complain that there has been cherry-picking. But these errors seem to be more material. They move the dial more than is typical,” says Mark Jacobsen, a professor of economics at the University of California at San Diego.

The mistakes are not the only problem for the Trump proposal. On Friday, Honda and General Motors broke ranks with other automakers and signaled unease about the rollback, with Honda openly opposing it. The car industry had previously stood united in supporting the Trump administration.

But it’s the math errors, and not the loss of corporate support, that could prove most damaging long-term for the rollback. Jonathan Adler, a law professor at Case Western Reserve University and a conservative commentator, told me that simple errors can imperil a regulation in court.

Read: The car industry squirms, as it gets what it asked for

The errors that appear to exist in the Trump proposal are “the kind of thing that an agency would clearly be under a legal obligation to address, and what I think any reviewing judge would raise an eyebrow about,” he said. “The easiest way to make a court pay attention is to raise this sort of question.”

The rollback’s fate will hinge on how the Environmental Protection Agency and the Department of Transportation, the federal agencies overseeing the rollback, respond to the errors and fix them, he said.

But this may prove difficult. In some cases, the mistakes are so large—and so central to the rule’s legal justification—that remedying them may destabilize the entire argument for the proposal. Public documents also make it clear that the Trump administration knew about some of the errors before the rollback was published.

Neither the EPA nor the Department of Transportation responded to a request for comment.

Trump officials have made one overarching pitch for their fuel-economy rollback. They’ve insisted that the new rules are much safer than what’s come before—so much safer, in fact, they named their proposal SAFE. But under scrutiny, many of these safety benefits vanish into air.