Sen. Tom Coburn (R-Okla.) reveals his "Back in Black" plan to reduce the federal deficit. (J. Scott Applewhite/Associated Press)

1) Sen. Tom Coburn (R-Okla.) has long been politically opposed to the Affordable Care Act. As recently as Monday, he offered a major repeal-and-replace plan. Now, he has a more personal grievance against Obamacare: Coburn, who is undergoing treatment for prostate cancer, says he lost coverage for his oncologist when he purchased a plan on the new health exchange.  “I’m doing well from a health standpoint, got great docs,” Coburn said Tuesday morning in an interview on MSNBC.  “Fortunately, even though my new coverage won’t cover my specialist, I’m going to have great care, and I have a great prognosis.”

2)  Coburn's story isn't necessarily a unique one about Obamacare, although it is definitely higher-profile, given that he's a senator in the middle of cancer treatment. There are other people buying insurance from the health law's new programs who are finding that their new policies come with a different provider network that doesn't include their current doctor. We don't have a good estimate on how often this has happened because there's no national database listing which people have access to which doctors. We know that this has occurred mostly from anecdotes that turn up in local and other news reports.

3) No, these stories are not made-up, Republican hype. But they're also not a unique result of the Affordable Care Act. They're partly a product of how insurance markets worked before the health care law and how they work after it. Whenever anyone switches insurance plans -- such as by changing jobs, by moving from the individual market to Medicaid or by turning 65 and aging into Medicare coverage --the new coverage comes with a new set of doctors. Even if I switched between the two health insurance options offered here at The Washington Post, I would have to find a different physician within my new network. 

4) There is one aspect of this situation that can be linked more directly to the new health law:  The plans sold through the Obamacare exchanges tend to have relatively limited provider networks. A recent McKinsey report that found that 70 percent of the products offered on the exchanges are either "narrow" or "ultra-narrow" products, meaning they include fewer than 70 percent of the local hospitals in their networks.

Part of this has to do with the Affordable Care Act, under which insurance plans are competing against one another on the price of their premiums and only have so many levers to stay competitive. There's not a ton of wiggle room to change the benefit package; the health care law mandates that insurers cover a pretty broad set of medical services. By law, insurance plans cannot jack up the prices for more expensive consumers, either. So one of the few powers they can exert is limiting their network to a smaller set of providers.

5) This can lower costs in two ways. First, when insurance plans limit their provider network, they can generally exert lower prices from those doctors and hospitals. It's like buying in bulk: They're promising physicians a whole lot of patients and negotiating lower rates in return. Second, there's lots of variation in health care prices, and narrow network plans tend to (but don't always) contract with those that charge lower prices. It's worth noting here that most academic research fails to find a relationship between the quality of providers and their prices; expensive doctors can be equally as good or bad as cheap doctors.

6) But here's where things get more confusing: The move to narrow networks also pre-dates Obamacare. Employers, for example, were already gravitating toward these types of plans as insurance premiums ate up an increasingly bigger chunk of their budgets. 

This makes it hard to tease out how much of the narrowing of networks in 2014 has to do with the health care law, and how much is a continuation of pre-existing trends in the insurance market.

7) Look at how Kaiser Family Foundation describes these type of plans in the graph above. They call them "high-performance provider networks." That's the other, more positive way to think about these more restricted plans. In a best-case scenario, they include a network of doctors who work more closely together to deliver coordinated, high-quality care. The best example of this is probably Kaiser Permanente (which is not affiliated with Kaiser Family Foundation), one of the top-ranked health plans that limits patients exclusively to seeing the doctors that they employ. Patients are generally okay with that model because they're satisfied with the small number of hospitals and physicians they do get to choose from.

8) So, did Coburn lose his oncologist because of Obamacare? One detail that I haven't been able to track down - I've sent an inquiry to Coburn's office - is whether there were any exchange plans that included his doctor in network. If there weren't, then it seems fair to agree that the senator did lose insurance coverage for this particular doctor because of the health care law. Would he have lost this doctor in a world without Obamacare that was already moving toward narrow networks? It's a possibility, but we can't know for sure.

9) If a lot of patients end up in similar situations and become frustrated with the lack of choice on the exchanges, we could see a backlash against the exchange plans. This would be something akin to what happened in the mid-1990s, when patients pretty much revolted against limited-choice Health Maintenance Organizations, or HMOs. Insurers added more provider choice into their networks in response, and health care costs started growing at a faster pace shortly after.

10) There's a trade-off that Americans on the individual market will have to work through in the coming months and years. Theyll have to think about whether they want to pay higher premiums for products with more choice. If consumers start gravitating toward higher-cost plans with bigger networks, you can bet insurance companies will offer more of them. But if they stick with their cheaper insurance products -- and decide they're okay with switching doctors to nab that lower price --then these type of products could increasingly become the norm in the market.