The part of Paul Ryan’s budget that’s going to get the most attention is his proposal to privatize and voucherize Medicare. But the part that worries me the most is his effort to slash Medicaid, with no real theory as to how to make up the cuts.

Ryan’s op-ed introducing his budget lists Medicaid under “welfare reform,” reflecting the widespread belief that Medicaid is a program for the poor. That belief is wrong, or at least incomplete. A full two-thirds of Medicaid’s spending goes to seniors and people with disabilities — even though seniors and the disabled are only a quarter of Medicaid’s members. Sharply cutting Medicaid means sharply cutting their benefits, as that’s where the bulk of Medicaid’s money goes. This is not just about the free health care given to some hypothetical class of undeserving and unemployed Medicaid queens.

That’s why it’s well understood that converting Medicaid into block grants means cutting people off from using it, or limiting what they can use it for. You can see CBO director Doug Elmendorf say exactly the same thing here. There’s just not another way to cut costs in the program. You can, of course, work to cut costs outside of the program, either by helping people avoid becoming disabled or making it cheaper to treat patients once they become disabled or sick, but those sorts of health-system reforms are beyond the ambitions of Ryan’s budget.

To get around some of this, Ryan’s op-ed talks about state flexibility, with the implication being that states have some secret Medicaid policies they’ve been dying to try but that the federal government simply hasn’t let them attempt. But the truth is there’s been a tremendous amount of experimentation in Medicaid over recent decades. Indiana converted its Medicaid program into health savings accounts. Tennessee based its program around managed care. Massachusetts folded its Medicaid money into Mitt Romney’s health-care reforms. Oregon tried to rank treatments by value. Some of these reforms have worked well and some haven’t worked at all, but none have solved the basic problem that covering the sick and disabled costs money, and you can’t get around that by trying to redesign their insurance packages. For that reason, block-granting Medicaid ultimately means cutting health-care coverage to the poor, the elderly and the disabled, even as it doesn’t actually address the factors driving costs throughout the health-care system.