President Trump knows that the rally crowds — both in the real world, and in his head — erupt in cheers whenever he boasts of reversing something Barack Obama accomplished, and now he’s about to try to roll back one of the biggest pieces of Obama’s legacy: the fuel economy and greenhouse-gas emissions standards for passenger vehicles.

You cannot overstate the importance of this move. But here’s the thing: Soon enough, the process will require the Trump administration to show its cards in terms of the impact of this change. And once this happens, it is likely to be a tough sell politically — provided that the administration doesn’t try to game this process and suppress good data, which, given its track record, is a plausible possibility.

The New York Times reports that the Environmental Protection Agency will soon announce a new proposal weakening the efficiency and emissions standards on cars and light trucks. As the Times notes, this is a “victory” for “car manufacturers.” But EPA chief Scott Pruitt intends to present the policy as a boon to consumers, by claiming (in the Times’s words) that it will eliminate a “regulatory burden on automakers that will result in more affordable trucks, vans and sport utility vehicles for buyers.”

Environmental Protection Agency Administrator Scott Pruitt said the EPA will open up a national debate on climate change in 2018. (Reuters)

We don’t yet know the specifics of the proposal in terms of how dramatically it will roll back the standards put in place under Obama. The Post, which reported on this yesterday, notes that the administration is currently consumed by internal wrangling over the question.

But two sources who have seen the plan tell the Times it will “substantially” roll back standards. Those standards would currently require fleets of vehicles to attain an average vehicle standard of 54.5 miles per gallon by 2025, reducing carbon dioxide emissions by billions of tons throughout the lifetime of all the vehicles impacted.

Rolling these standards back “substantially” would be a big, big deal. It would mean that Trump is undoing a big chunk of progress, by gutting an enormously important initiative at the heart of the U.S. effort to combat carbon dioxide emissions — and global warming.

“Right now, cleaning up cars is the biggest step that the United States is taking to curb its carbon pollution,” David Doniger, a senior analyst at the Natural Resources Defense Council, told me this morning. “Now they’re taking a whack at that. This would cripple the biggest step we’re taking to do our part in fighting climate change.”

But this is likely to create a political problem for the Trump administration. And it also raises a possibility that we need to be watching out for.

These Obama-era standards were promulgated under the Clean Air Act, which mandates that the EPA regulate carbon emissions for the public health. But as Christy Goldfuss, a senior vice president at the Center for American Progress, points out, this also means that federal law requires the EPA to present a cost-benefit analysis that will show the policy’s actual impact and justification.

The administration’s rationale for the change is going to be that it will reduce the costs of vehicles, thus creating a boon to consumers. But that doesn’t take into account the higher sums that consumers will have to spend on gas to power less-fuel-efficient cars. A cost-benefit analysis will thus be revealing on this front: It will have to tell us how much less-fuel-efficient cars will be over time, relative to current policy, and how much that will mean in increased carbon dioxide emissions.

“The EPA is required to show how much carbon dioxide will be produced by the rollback of fuel efficiency targets,” Goldfuss told me. “From the moment we see their proposal, we will know the predicted impact and whether it is based on sound science and analysis.”

And that creates still another possibility: that the administration won’t base this analysis on “sound science and analysis.” We’ve already seen the laughably slapdash rollout of the thinly veiled Muslim ban, which ignored two internal Homeland Security Department analyses that badly undercut its national security rationale. We’ve already seen Trump justify his border wall by saying it will stop drugs from pouring in, even though experts say this is nonsense. We’ve already seen the White House cut the number of refugees admitted into the United States after deep-sixing internal data that showed refugees are a net fiscal plus.

This very well may happen again, and if so, it will be plainly obvious. By contrast, if the administration produces a real analysis, it will likely reveal any substantial rollback of these standards, from a cost-benefit standpoint, as utter folly.

Trump says this change will allow us to “make cars in America again,” which means he’ll sell it with the usual #MAGA rhetoric, as if reversing the progress being made away from dirty, gas-guzzling vehicles will be seen as a restoration of greatness. But environmental regulations are popular, and large majorities are concerned about climate change. So most Americans are more likely to see this as going backward.

They told him they didn’t need his cooperation against Manafort, according to a person familiar with the investigation, and instead wanted to hear what he knew about contact between the Trump campaign and Russians.

Gates allegedly knew that his and Manafort’s business associate had ties to Russian intelligence. This suggests Mueller wants to know what transpired between the Trump campaign and Russia via him.

Pruitt’s lease at a Washington apartment owned by a lobbyist friend allowed him to pay $50 a night for a single bedroom — but only on the nights when he actually slept there. White House officials are growing dismayed about the questions surrounding Pruitt’s living arrangement, including his initial inability to produce any documentation about his lease or his actual payments, according to three officials.

EPA’s counsel says the arrangement is kosher, which is odd, given the White House’s worry about it.

* SILICON VALLEY STARTS TO LIKE TRUMP: The New York Times reports that the top tech companies, which recoiled at Trump’s election, have quietly found things to like about his presidency:

Quietly, the tech industry has warmed to the White House, especially as companies including Alphabet, Apple and Intel have benefited from the Trump administration’s policies. Those include lowering corporate taxes … and, so far, ignoring calls to break up the tech giants. … And Mr. Trump let die an Obama-era rule that required many tech start-ups to give some workers more overtime pay.

Yep, Trump is really sticking it to those elite cultural liberals.

* TRUMP’S VETERANS AFFAIRS PICK ‘DEEPENS DISARRAY’: Trump announced by tweet that he was replacing the head of the Department of Veterans Affairs with his personal physician. Politico reports:

The timing … surprised his own chief of staff and knocked the government’s second-largest agency, already bedeviled by scandal, deeper into disarray.  The tweet was big news — not just to the public, but to some senior aides, according to one White House official.

Politico adds that veterans worry Trump’s replacement “could be installed as a figurehead, leaving lower-level appointees to steer the agency toward privatization.” That process, no doubt, will also be scandal-free.

Post Opinions writers and editors discuss what's behind Trump's personnel changes at the Department of Veterans Affairs. (The Washington Post)
His résumé lacks the type of management experience usually expected from the leader of an agency that employs 360,000 people, has a $186 billion annual budget and is dedicated to serving the complex needs of the country’s veterans. … A senior White House official described an informal interview process, without the extensive vetting that typically accompanies a Cabinet selection.

But Trump probably “went with his gut,” so it’ll all be good.

* NO SUNLIGHT ON SPENDING BILLS NOW THE NORM: Trump raged about having to sign an omnibus spending bill with little public debate (not the real reason he was angry, of course). Carl Hulse makes an interesting point about why this is now the norm:

The Senate … has essentially given up on … considering individual spending bills on the floor after they have been hashed out in committee. The threat of a slew of politically charged amendments, the need for 60 votes … and the reluctance of the leadership to devote the necessary floor time to debate the bills have effectively ended public review of the 12 annual spending bills by the full Senate.

As Hulse also notes that congressional leaders have added incentive to do this, because it maximizes their own power.

* AND INGRAHAM’S APOLOGY SHOWS POWER OF PARKLAND KIDS: Right-wing personality Laura Ingraham has apologized for a tweet sliming David Hogg, a lead Parkland kid, after an online campaign targeting her advertisers. The Post reports:

Hogg’s push for Ingraham’s advertisers to respond to her comments worked remarkably quickly. The swift results showcase the power that the Parkland survivors have, not just in organizing rallies but in spurring corporate America to act.

Of course, the only thing that will ever get Congress to act on gun violence is to vote out Republicans and replace them with Democrats, so let’s hope the kids sustain this energy through November.