The budget that President Trump proposed Monday takes a hard whack at the poorest Americans, slashing billions of dollars from food stamps, public health insurance and federal housing vouchers, while trying to tilt the programs in more conservative directions. The spending plan reaches beyond the White House’s own power over the government social safety net and presumes lawmakers will overhaul long-standing entitlement programs for the poor in ways beyond what Congress so far has been willing to do. The changes call on lawmakers to eliminate the expansion of Medicaid under the Affordable Care Act and transform the rest of that...