Republicans have long fumed about the federal government’s role in health care, ever since Medicare for the elderly and Medicaid for the poor were both passed in 1965. Now, though, we’re at a crossroads, where a frontal assault on Medicaid could cause big damage to both programs.

The temptation for too many Americans, as I’ve written before, may be to skip over the Medicaid-related parts of the GOP proposals to repeal and replace the Affordable Care Act, aka Obamacare. That would be wrong because those parts of the American Health Care Act, aka Trumpcare, may be the most radical and will be detrimental to the poor, working poor, children, sick, disabled, and seniors. They will hit many millions more middle-class Americans than might be thought.

Opponents also say that Trumpcare and its Medicaid and health insurance changes will harm Medicare, the linchpin of health care coverage for seniors.

One of the big challenges in the GOP assault lies in details of how Medicaid works, who qualifies for its benefits, and how the federal government works with states to pay for it all. Most Americans’ eyes likely glaze over when lawmakers argue over block grants and per capita allocations and similar bureaucratic verbiage. Republicans also, smartly, have tried to defer some of the effects of their Medicaid attack for a few months or a few years, so they won’t add to the already formidable opposition to their attack on Obamacare now. President Trump, though, may try to accelerate Trumpcare’s Medicaid changes.

Here’s the bottom line, though: Millions more Americans under Trumpcare will lose health coverage due to Medicaid changes. This is beyond the millions who will be affected under Trumpcare’s health insurance changes. The poor and working poor will be hard hit by Medicaid under Trumpcare. President Trump and the Congress will provide a lot less federal assistance to states to help them deal with their sick, old, and disabled. This could be financially catastrophic to state and local budgets as officials from Juneau to Tallahassee must make tough choices with fewer resources. The nation will be riven, with Americans’ health care increasingly dependent on the kismet of where they live.

It starts like this, as the New York Times explains:

House Republicans are proposing to fundamentally alter the way the federal government has been financing Medicaid for more than 50 years.  … Medicaid provides health insurance to 74 million people, or one in five Americans. Of the 20 million who gained insurance under Obamacare, at least half were through Medicaid expansion. The changes would not begin until 2020. But the long-term impact on states would be unequal, with some faring better than others . … The Republican bill calls for capping how much the federal government gives each state per Medicaid enrollee, based on how much the state was spending on the program in 2016. .. Since it was created in 1965, federal funding for Medicaid grew as needs changed for the states. If more people became eligible, say, because of a recession, or if costs rose because of expensive new medicines or a public health crisis, states received more federal money. Federal spending on Medicaid flexes as states alter their policies, eligibility rules and payment rates for doctors, hospitals and nursing homes. … Under the Republican plan … federal funding for every Medicaid beneficiary would essentially freeze, rising only with the medical component of the Consumer Price Index, or the price of medical care.

What the federal government effectively will do is to shift hundreds of billions of dollars in Medicaid costs down to states. They not only would be forced to make up this difference to sustain their programs, they would lose even more because they likely would shrink them, losing out on federal help for growing programs. At least eight “trigger” states expanded Medicaid but only as long as they got expanded help under Obamacare. They have said they will reverse their expansions if the AHCA strips the extra help away.

Further, there are Medicaid rule changes throughout Trumpcare, and some make it harder for recipients to get or to keep coverage or to get maximum benefits under the program. They may struggle, for example, to get and stay enrolled, simply because their lives lack the stability required by new rules—Medicaid recipients churn off and on the program because they are seasonal workers or because they have and lose low-paying jobs more readily than well-educated, highly people might. Children, who are among the biggest beneficiaries of Medicaid, may be shifted under new rules to programs that are cheaper and offer them less support. Trumpcare slashes a benefit that allowed Medicaid recipients some retroactive coverage. This is key for patients who, for example, might be hospitalized for treatment of a condition, which they find that had caused their health to decline and cost them for medical services that they might have thought would be covered.

Trumpcare also will roll back Medicaid requirements and programs for mental health and addiction, stripping patients and states of what advocates say are invaluable ways to combat an epidemic of opioid drug abuse.

AARP, the nation’s largest advocacy group for Americans older than 50, has assailed Trumpcare’s Medicaid plans. The group says that reducing its funding and pushing Medicaid down to the states fails to reckon with the nation’s graying population, sizable numbers of whom rely on the program for independent living or financial support in nursing home care. AARP also fears that cuts in Medicaid will create even greater drains and destabilize Medicare.

GOP senators in states that expanded Medicaid under Obamacare—prodded by Republican governors— may become a big problem for Trumpcare’s passage. If nothing else, they may insist that the more deliberative Senate actually dives into the GOP health proposals and determines, fully and officially, the measure’s costs and effects.

Although President Trump and congressional Republicans have been railroading Trumpcare through, at the least lawmakers and all the rest of us need a clear, complete understanding of how some complex Medicaid changes likely will be detrimental to so many. Our health and wellbeing is hugely at stake and it’s critical we not take speedy, cruel, short-sighted steps now.