The proposal would raise military spending by 14.1 percent while cutting funding for the State Department — the agency that has a mandate to resolve problems without going to war — by 26.9 percent. It would cut the Department of Health and Human Services by 20.3 percent and the Department of Education by 10.5 percent. It calls for (yet again) the repeal of the Affordable Care Act and proposes cutting food stamps by $213 billion, or around 30 percent, over 10 years. Medicare and Medicaid, which benefit one-third of Americans, are targeted for cuts of hundreds of billions of dollars.

If Congress adopted Mr. Trump’s proposal, millions of people would stand to lose health insurance, subsidized food, low-cost housing and other benefits. The result would be to greatly increase poverty and hunger in America.

This is surely not what most of Mr. Trump’s working-class supporters imagined during the primary and general election campaigns. In May 2015, Candidate Trump tweeted, “I was the first & only potential GOP candidate to state there will be no cuts to Social Security, Medicare & Medicaid.” And in an April 2016 ad that ran in Pennsylvania he promised to “save Social Security and Medicare without cuts.”

But wait, there’s more. Another of Mr. Trump’s promises was to build the “gleaming new roads, bridges, highways, railways and waterways all across our land,” a promise that he referred to as recently as his State of the Union address in January. Yet his budget recommends slashing funding for Amtrak and grant programs that help local and state governments pay for highway and transit projects. Over all, the administration wants to reduce the Department of Transportation’s budget by nearly a fifth. The budget would also effectively cut the Highway Trust Fund by $122 billion over a decade.

No doubt Mr. Trump will claim he is still serious about infrastructure by pointing to a separate infrastructure proposal he announced on Monday. In that document, the administration says it will bolster investment by $1.5 trillion over 10 years. But the math simply doesn’t add up. The White House suggests that the federal government would put up only $200 billion, which would be enough to get state and local governments and the private sector to supply the rest of the money. But where would most cities and states find those funds? Already strapped, many will struggle to raise new tax revenue, because the Republican tax law limited the deductibility of state and local taxes. The private sector might be interested, but only in projects like toll roads that produce a steady and rich source of income.