The supposed implosion of the Affordable Care Act’s private insurance markets looks more and more like a manageable, geographically limited problem ― one that policymakers could fix pretty easily, if only some of them weren’t trying so hard to undermine the program.

The latest development comes out of Nevada, where until last week 14 counties had no options lined up for the state’s insurance exchange in 2018. Centene, which already offers policies in parts of Nevada, announced on Tuesday that it would expand next year to offer policies statewide ― which means roughly 8,000 exchange customers in those 14 counties will have a way to buy the Affordable Care Act’s regulated, subsidized policies.

Those thousands of people would have been stuck looking for some other source of insurance had their counties remained “bare,” with no carriers on the exchange. And because people buying policies through the exchanges don’t typically have access to employer-sponsored plans or qualify for government programs, most of those people would have ended up with no coverage at all.

The problem of bare counties has gotten a lot of attention in the last few months. Many insurers have scaled back their presence in the new Obamacare markets, citing their inability to make a profit because they can’t attract a stable mix of healthy and sick customers. Republicans have repeatedly said this exodus is a sign of the program’s collapse, and a reason to repeal the health care law.

House Speaker Paul Ryan (R-Wis.) once called repeal an “act of mercy” because, he said, the program’s new markets would fall apart without intervention.

But even as most of the big, commercial carriers like Aetna and Cigna have beat a hasty retreat from Obamacare, carriers like Centene have filled in the gaps. At this point, only two counties nationwide have no carriers lined up for next year. One is in Ohio, the other in Wisconsin. Together they account for roughly 400 customers, and it’s not too late for those counties to get insurers, too.

ACA marketplaces work well in densely-populated liberal areas. The marketplaces require more care and feeding to really succeed in Wyoming, Iowa or Oklahoma. Harold Pollack, University of Chicago

That doesn’t mean everything is hunky-dory. Centene’s business model relies on narrow physician networks to keep premiums down, which isn’t what all consumers would prefer. And although the number of truly bare counties has now shrunk to nearly zero, there are still many that only have one insurer. Roughly 40 percent of all counties will have just one exchange insurer in 2018, according to the latest figures from the Department of Health and Human Services.

But even that number is a little misleading, because those counties are disproportionately rural. In other words, not that many people live in them.

This isn’t surprising. Rural counties are inherently difficult for insurers to manage, because the low numbers of customers make it difficult to get that ideal mix of healthy and sick enrollees ― and because the relative paucity of doctors, hospitals and clinics makes it impossible for insurers to play providers off of one another to get lower prices. This was true before the Affordable Care Act was passed.

To put all of this in perspective ― to show just how many people will really feel the effects of dwindling insurance options, and which parts of the country they call home ― Harold Pollack, a social scientist at the University of Chicago, and Todd Schuble, a computational scientist there, drew up two maps. They originally posted them at healthinsurance.org and have since adapted them for HuffPost.

One map shows counties with standard geographic borders. The area covered by counties with just one insurer is substantial.

Harold Pollack and Todd Schuble

The second map adjusts county size for population. In it, the portion of the country with just one exchange carrier is smaller, because those rural counties shrink quite a bit.

Harold Pollack and Todd Schuble

One pattern evident in both the original and the population-adjusted maps is where these counties with just one insurer tend to be: in the South and some parts of the interior West.

Partly that’s a function of population distribution. Those are the parts of the country with the most rural territory. But partly that’s a function of politics. Those are also the parts of the country where conservative Republicans, the ones most opposed to the Affordable Care Act, hold the greatest political sway.

And that almost certainly makes a big difference. The law has tended to work best in places like California and Michigan ― states where officials have promoted the program and acted swiftly to address problems as they have come up.

“ACA marketplaces work well in densely populated liberal areas,” Pollack said in his healthinsurance.org article. “The marketplaces require more care and feeding to really succeed in Wyoming, Iowa, or Oklahoma. Competition among insurers and providers is pretty thin in these locales.”

Nevada is a prime example of this. The exchange has worked well in the metro areas, including Las Vegas. The 14 counties that were at risk of going bare are predominantly rural. One reason they have coverage now is that state officials ― including Gov. Brian Sandoval, who is a Republican but has also said he’s committed to protecting people’s insurance ― made it their business to attract new carriers

If more state or federal officials were committed to making the law work, they could make inroads as well ― if not by courting insurers, then by passing new regulations and laws to shore up the law’s weak spots.

There’s no shortage of ideas on the table. One possibility would be to create new “reinsurance” programs, which subsidize the consumers with the most serious medical problems. (Alaska and Minnesota have already done that.) Another possibility would be expansions of Medicaid, Medicare or the federal employee health plan, any of which could add insurance options in places that have too few.

Some of these ideas would do more that merely stabilize markets. They would make health care more affordable for the millions who still can’t pay for it easily, a problem that even most Obamacare defenders concede the law did not fully solve.

To be successful, policymakers would have to commit to fixing the law’s problems. But some key Republicans, including President Donald Trump, seem determined to do the opposite ― to repeal the law or to undermine it through sabotage, perhaps bringing about the very kind of crisis they claim is taking place already.