President Trump’s first budget, which he and his budget director claimed would erase the federal deficit within 10 years, would do no such thing, the Congressional Budget Office concludes in a new analysis.

The cuts in the president's budget would, the CBO finds, dramatically reduce the deficit, by about $4.2 trillion over 10 years (more than the $2.4 trillion in deficit reduction in Obama’s final budget). But even with those cuts, the total deficit would only be reduced by one-third rather than wiped out completely, as the Trump administration had claimed.

The CBO’s deficit reduction estimate is so much lower because the White House claimed its budget would lead to 3 percent economic growth, dramatically increasing tax revenue and closing the gap between what the government brings in and what it spends. But the CBO found that Trump's budget would only mildly improve economic growth. The average economic growth rate would rise by 0.1 percentage points per year, from about 1.8 percent to 1.9 percent.

The deficit reduction, meanwhile, would come at the cost of massive cuts to social safety net programs. Federal spending on health care would fall by 13 percent, a $1.9 trillion cut implemented by repealing the Affordable Care Act and then adopting another $610 billion in cuts to Medicaid. Food stamps (or SNAP) would be cut by 21 percent. Spending on international affairs programs at the State Department and elsewhere would fall by 32 percent, environmental and natural resource programs by 21 percent, and community and regional development programs by 37 percent.

And the report is almost certainly too optimistic. While it includes the reduction in revenues caused by repealing the Affordable Care Act, the CBO analysis does not include the Trump administration's tax reform proposals, which could cost upward of $3.4 trillion over 10 years according to the Tax Policy Center.

"That proposal lacked the specificity necessary to evaluate any effects from such a change," the CBO report writes. "For that reason, CBO and JCT used as a placeholder the administration's estimate that the proposal would have no net budgetary effect."

This is an unusual CBO report

It’s customary for the CBO to release an analysis of the president’s budget request. Budget numbers are quite sensitive to assumptions about future economic growth, population growth, aging, and more.

The White House also estimates the effects of its budget requests through its own budget shop, the Office of Management and Budget. But those estimates differed much more sharply for Trump’s budget than they did for President Obama’s or Bush’s. Obama’s budget office found that his last budget would cut the 10-year deficit by $2.9 trillion; the CBO found the number was $2.4 trillion.

That $500 billion split is a much smaller difference than the gap between the Trump budget office and the congressional office, which amounts to a difference of $3.7 trillion.

That’s because Trump’s OMB projected that the administration’s policies will result in an economic growth rate of 3 percent, far above the 1.8 percent growth the CBO is forecasting for the next 10 years. Most economic forecasters, be it at the Federal Reserve or at private banks, are closer to the CBO, and 3 percent growth is well outside what credible sources project, especially when the Trump administration’s crackdown on immigration is suppressing labor force growth.

In a Wall Street Journal op-ed, OMB Director Mick Mulvaney described the growth assumption as “MAGAnomics.” "If the Trump administration has one overarching goal, it's to Make America Great Again," the op-ed reads. "But what does this mean? It means we are promoting MAGAnomics — and that means sustained 3 percent economic growth."

The CBO report also comes at a time when the White House and congressional Republicans are conducting an unprecedented assault on the nonpartisan budget analysis agency’s integrity. On Wednesday, the White House's official Twitter account sent out a "fact-check" video trying to debunk the CBO's findings that Republican health bills will reduce health coverage by more than 20 million people; the video was captioned "The Congressional Budget Office's math doesn't add up," and at one point the video misspelled the word "inaccurate."

In an interview in May, Mulvaney similarly attacked the group, saying, “At some point, you've got to ask yourself, has the day of the CBO come and gone?”

The CBO’s current director, Keith Hall, is a Republican who served in the Bush administration, was hand-picked by congressional Republicans for the job in 2015, attacked both the minimum wage and Obamacare in print before his appointment, and earned praise from Trump's own health and human services secretary, Tom Price, who as House Budget Committee chair helped pick Hall for the CBO job and commented at the time that he "will bring an impressive level of economic expertise and experience to the Congressional Budget Office."

It’s likely that the White House’s response to the CBO’s latest report will continue the pattern of trying to delegitimize the agency and its findings. But the report’s actual contents are remarkably damning all the same.