Halbig v. Burwell, the case in which opponents of the Affordable Care Act won a dramatic if temporary victory yesterday, has profound implications for millions of Americans’ health care. But it’s also a demonstration of a trend that is determining more and more of what our politics and our country are going to look like in future years.

We talk a lot about America being divided ideologically, with liberals and conservatives increasingly distrustful and dismissive of each other. But we’re also in the process of creating two different nations, where stepping across a state border means entering a society with profoundly different laws and policy goals. And Republicans may have just stumbled on a way to use the federal government to increase that division.

Both parties are driving this broad movement. In many Republican-controlled states, it’s now all but impossible for a woman to get an abortion; people are encouraged by the state government to bring their guns to church and into bars; and taxes are whittled away while social services are slashed. Democrats too have gotten more aggressive in places they control, on issues like raising the minimum wage, same-sex marriage, and legalizing marijuana.

But the challenges to the ACA have shown the Republicans a new path, a kind of federalized federalism, where they can not only make Red America a more conservative place through state laws, but exempt Red America from federal laws they don’t like.

This wasn’t part of a carefully laid-out plan. Initially Republicans were just using any and every means they could find to undermine the ACA, with the goal of destroying it completely. Though they failed to do that, they won their first significant (if partial) victory when the Supreme Court ruled that states could opt out of the law’s expansion of Medicaid, which meant that we have two different countries when it comes to health coverage for poor people. If you’re poor and you live in a blue state or one of the few red states that has accepted the expansion, you can get free health insurance. If not, you’re out of luck. See, for instance, this vivid New York Times article about the city of Texarkana, which lies half in Texas and half in Arkansas; whether you get health insurance is determined by which side of town you live in.

In the Halbig case, conservatives located a drafting error and pursued it for no reason other than that it looked like a promising vehicle for Republican-appointed judges to strike a blow at the law. Creating two different countries when it comes to the ACA wasn’t really the goal, but it could be the outcome.

Let’s imagine the Supreme Court upheld the D.C. Circuit panel’s decision. In the states that have already established state exchanges, nothing would change. With a few exceptions (like Kentucky and Idaho) these are blue states. Everywhere else, people would immediately lose the tax credits they received to buy insurance, reverting to the pre-ACA status quo. That means more people without insurance, and a system that is generally more cruel and unforgiving. The states that are Democratic-controlled or divided but haven’t yet set up an exchange, like Pennsylvania, New Jersey, and Maine, would probably move to do so in order to restore those subsidies to their citizens. Once it all shook out, you’d have a situation in which, for all intents and purposes, the most consequential social legislation passed through Congress in nearly half a century was operative in only half the country.

If that were to happen (and maybe even if it doesn’t), Republicans are likely to see a new means to accomplish their policy goals on any number of issues. If you can’t repeal a federal law you don’t like, maybe you can have it apply only to Blue America. Get a few creative lawyers together, and you can come up with a rationale for a lawsuit to allow states to opt out of almost any law; few can deny now that no matter how thin the legal reed you hang such a suit on, there will always be conservative judges who will embrace your logic. We could see a proliferation of opt-out amendments in Congress, as each significant piece of legislation is accompanied by an effort to give Republican states the ability to exempt themselves.

And don’t be surprised if perpetually vulnerable red state Democrats end up supporting those amendments from time to time, so they can give their party the votes it needs to pass bills, but also tell the folks back home that they stood up for states’ rights.

In 1932, Justice Louis Brandeis wrote in a dissenting opinion:

It is one of the happy incidents of the federal system that a single courageous state may, if its citizens choose, serve as a laboratory; and try novel social and economic experiments without risk to the rest of the country.

But the assumption has always been that when states act as laboratories of democracy, they’re exploring different ways to arrive at common goals. Increasingly, liberals and conservatives can agree only on the most abstract goals, like prosperity and freedom, but on almost none of the specifics. With the ACA as an example, Washington could become the new laboratory of division, where federal legislation and federal lawsuits become the means to drive Red America and Blue America further apart.