Before Obamacare, Washington kept its checkbook for Medicaid fairly wide open. The federal government set the minimum guidelines for who had to be covered by the program, but states could be more generous if they chose, so long as they stayed within certain guidelines. Some (think New York) tried to provide coverage to as many of their residents as possible. Others (think Florida) shot for far fewer. Health care reform opened up the checkbook even further. By expanding the program to cover childless, able-bodied adults for the first time, it lifted some of the last meaningful limits on Medicaid's largesse, other than the desire of states to shoulder their portion of the expense.

Under Ryan's proposal, Washington's open-ended commitment to helping the poor get care would be history. Instead of offering them unlimited funding, the federal government would hand each state a fixed sum of money -- or a "block grant" -- to cover the poor and uninsured as they saw fit. On its own, that change wouldn't necessarily devastate the program. But here's the key detail, the trick that yields all those budget savings conservatives are after: The grants would be indexed to grow much slower than healthcare costs.

The point is to make them stingier over time. Conservatives hope that will force states to find new efficiencies. More likely, it will just lead them to insure fewer residents, offer less generous coverage, or both. In essence, every state would have to act more like Florida, and less like New York. The graph below, from a study published last year by the Urban Institute and the Kaiser Family Foundation, shows the growing gap between Ryan's spending for Medicaid, and the program's growth with or without Obamacare.

Even without conservatives looking to slash the program, Medicaid is about to begin a somewhat awkward transition phase. Credit the Supreme Court. The health reform law attempted to guarantee insurance to an additional 17 million Americans by requiring states to cover any adult living on less than 138 percent of the federal poverty level, or about $31,000 for a family of four today. But in its decision upholding most of the law, the justices ruled that states could choose to opt out of the new mandate. Governors in some of the states which would have had to add the most residents to their rolls, such as Texas and Florida, have already said they won't take part.

Still, the Urban Institute's analysis gives us a sense of how many people would stand to lose their government care under Ryan's plan. Even if you ignore the effects of repealing Obamacare, his austere budget would still knock anywhere between 14 million and 27 million people out of the program. When you consider those who would lose coverage granted under health care reform, the total rises to between 31 and 44 million. In the end, we're talking about a potential cut of up to half the program.