PRESIDENT TRUMP released a proposal for fiscal year 2018 discretionary spending — the “skinny budget” — two months ago, and the $1.1 trillion plan garnered deservedly poor reviews. In a nutshell, Mr. Trump would have gutted the Environmental Protection Agency, the National Institutes of Health and similarly crucial domestic agencies to fund a big boost in defense spending and border security. On Tuesday the White House releases its ideas for the remaining $3 trillion or so in federal spending, including large-scale entitlements such as Medicaid, and the early indications are that the priorities embodied in this sequel will be no more humane or rational.

Not surprisingly, Mr. Trump has decided to embrace the House Republican health-care bill’s $800 billion in cuts to Medicaid (over the next decade), according to The Post’s Damian Paletta. To do this, he would apparently add cuts to other safety-net programs, including housing and Supplemental Nutrition Assistance Program benefits, also known as food stamps. The latter could be changed by enabling states to stiffen work requirements for those who receive the assistance. Such cuts are being contemplated, of course, at a time when Mr. Trump is also promising huge reductions in taxes, mostly for upper-income individuals and corporations. This reverse redistribution is unconscionable on its own terms. In addition, Mr. Paletta reports that the Trump budget documents may claim that tax cuts drive so much additional growth that they — plus the safety-net cuts — will restore federal budget balance a decade hence. Thus do warped budgetary priorities produce warped budgetary arithmetic.

The truth of the matter is that there can be no plan for long-term fiscal balance that does not include both enhanced revenue and reform of the two biggest entitlement programs in the federal budget, Medicare and Social Security, which together account for 39 percent of all spending. Yet Mr. Trump promised during the campaign not to touch these middle-class favorites, and his budget apparently honors that pledge — with the possible exception of Social Security’s disability program, which primarily helps low-income beneficiaries.

To be sure, federal safety-net programs should not be immune from pruning; we’ve called for many such measures in previous editorials. Social Security disability in particular could be adjusted to help people return to work sooner, without losing needed cash aid. Yet America’s poorest and most vulnerable people should be the last group called upon to sacrifice for the sake of deficit reduction, not the first — and certainly not the only. Fortunately, presidential budgets are notoriously ephemeral, as illustrated by the fate of the “skinny budget,” which was quickly dismissed on Capitol Hill. The policy vision it embodied was too upside-down, apparently, even for the conservative Republican majority. That view of the world does not improve through repetition.