A levee has been breached.

Republicans have battled government-funded health care since the day in 1965 when President Lyndon B. Johnson signed Medicaid and Medicare into law.

President Ronald Reagan cut the budget of both programs in 1981. President George W. Bush further trimmed Medicaid. In 1995, after taking over both houses of Congress for the first time in 40 years, Republicans tried but failed to convert Medicaid into a set of block grants to the states and eliminate poor people’s right to health insurance.

But despite the unremitting hostility of the GOP, government-funded health care not only survived but also continued to grow, becoming a bedrock of America’s social safety net. Federal spending on Medicare and Medicaid increased by nearly 90 percent in real terms over the 1990s, another 80 percent in the 2000s and nearly 60 percent in the 2010s. It rose by nearly 10 percent over the past five years.

And government subsidized insurance expanded beyond the poor and the old under President Barack Obama’s Affordable Care Act, which survived President Donald Trump’s attempt to dismantle the program in 2017 thanks to that last-minute thumbs-down from Sen. John McCain (R-Arizona). Trump then allowed states to require that Medicaid beneficiaries get a job — a practice that would bump millions off the program. But that effort, too, was shut down by Trump’s successor, Joe Biden.

Health care, or so it seemed, had become politically invulnerable — not unlike Social Security. Nips and tucks to Medicaid and Medicare might be okay. Yet, though other parts of America’s social safety net were successfully dismantled — including the Aid to Families with Dependent Children income support program for poor families killed during President Bill Clinton’s campaign to “end welfare as we know it” — health care appeared bulletproof.

Until now.

The One Big Beautiful Bill Trump signed on Independence Day will cut about $1 trillion from Medicaid over a decade — the largest ever pruning of the program — ultimately bumping nearly 12 million needy Americans off health insurance, according to Congressional Budget Office estimates. It also reduced subsidies for health plans under the ACA. Sequestration rules will require additional cuts to Medicare, totaling more than $500 billion.

The legislation suggests the United States is entering a new political equilibrium. If the government’s support for Americans’ health can be culled to this extent, the entirety of America’s social insurance net is in peril.

The GOP’s usual justifications are not credible. There is no evidence, for example, that demanding that Medicaid beneficiaries get a job — one of the ways the OBBB aims to cut spending — raises employment. The experience in Alabama, which added a job requirement to Medicaid in 2018 (ultimately stopped by a federal court), suggests that such rules just reduce enrollment, even among the employed.

Charging Medicaid with “fraud and abuse,” a common refrain in the Trump administration, glosses over the fact that Medicare and Medicaid are more cost-efficient than the nation’s astonishingly costly private health care system. Some states that expanded access to Medicaid under the ACA saw a decline in health spending. While fraud occurs, it is generally perpetrated by providers, not beneficiaries.

So why did the Big Beautiful Bill plunder the health care budget? Because that’s where the money is. Medicare and Medicaid account for over one fifth of government spending. Medicaid is the easiest to cut because its core constituency is poor and rarely votes.

And yet going after health care is nearsighted in the extreme. Americans, especially poor Americans, are notoriously unhealthy. The United States suffers among the highest rates of infant and maternal mortality, compared with affluent peers, the highest burden of chronic disease, the shortest life expectancy, and the highest rate of preventable mortality. Americans, nonetheless, see the doctor less often than other people in the rich world.

But what is perhaps most confounding is that by slashing health care spending, the GOP is targeting the well-being of part of its base — undermining the welfare of the aggrieved working-class coalition that brought Trump to power.

The GOP’s effort to reduce government support for health care is at odds with the trajectory of policy across pretty much every other rich country, where political incentives have put a priority on keeping citizens healthy and alive. It is also at odds with Trump’s political narrative. The proposition that he will protect beleaguered Americans from the ravages of globalization is in tension with a policy mix that cuts access to health care for the beleaguered.

Nevertheless, it might work. Trump and his fellow Republicans seem to think they can trim access to health care at no political cost because the disaffected Americans in their base want retribution more than government help during tough times.

They may be right. Political support for social insurance is weakening around the industrialized world, including among the robust welfare states of Western Europe, where it has been replaced by a demand to expel immigrants — undesirable consequences of a globalized world. A shift in U.S. politics might just be part of a broader realignment. The shift in U.S. politics seems to fit within a broader realignment.

If Trump and his fellow Republicans can convince their voters that they are getting even with the enemy — whether that means foreign countries, immigrants, the college educated or whatever — they could well get away with tearing apart what survives of America’s safety net.