Sen. Bernie Sanders’s campaign says Sen. Kamala Harris’s “Medicare-for-all” plan — one that establishes universal health care through both government-run and private health insurance — is “privatizing Medicare.”

“Her plan is centered around privatizing Medicare, enriching insurance executives and introducing more corporate greed and profiteering into the Medicare system — and even then, waiting for 10 years before any changes happen,” Faiz Shakir, the Sanders’s campaign manager, wrote in a fundraising letter to Sanders’s supporters.

Harris’s campaign strongly rejects this characterization. “Current Medicare includes private plans through Medicare Advantage,” Harris spokesperson Ian Sams said. “It’s just a misleading and false attack.”

Harris’s plan, released just ahead of the second Democratic presidential debate, has been panned by the original Senate author of Medicare-for-all. While Harris saw her stock rise after the first presidential debate, where she attacked Joe Biden’s record on race, she’s been less forthright on her true position on health care. She’s signed on to Sanders’s bill and backed abolishing private insurance, only to walk it all back. Her new plan clarified her distance from Sanders, but only seemed to only muddle the debate over Medicare-for-all further.

So does Harris support privatizing Medicare? No. Is her Medicare-for-all plan privatizing Medicare? Not outright.

Harris’s plan is designed around the current Medicare system, which already incorporates private insurance. She proposes that, over a 10-year period, everyone would transition to an expanded Medicare; she would allow for private insurance to play in a program structured like Medicare Advantage, which currently gives seniors the option to choose from a slate of private insurance options. It would cap out-of-pocket costs at $200.

This is markedly different from what Sanders has popularized as Medicare-for-all: a single-payer system that looks less like how Medicare actually operates today and more like something in Canada, where private insurance is essentially eliminated and every American is put on an expanded government-run program. The underlying principle of the Sanders plan is that private insurance, which operates on profits, can never truly incentivize care.

There’s a reason why the Sanders team is sounding the alarm bells here. Medicare Advantage has been riddled with scandal, taking government dollars to feed a for-profit health care industry. Just last year, federal investigators found the private plans denied claims “in an attempt to increase their profits.” It’s true that Medicare Advantage has played a significant role in expanding private insurance’s role in Medicare.

“This has been evolution, not a revolution, in Medicare: a quiet but persistent increase in private insurance in Medicare,” Tricia Neuman, a Medicare expert with the Kaiser Family Foundation, said of the current system. “Private insurers have been increasingly playing a role in the program.”

Harris promises her version of private plans would be strongly regulated. But whether her plan would see a continued expansion of private insurance within Medicare boils down to two questions that Harris’s plan doesn’t answer, Neuman says: 1) Will insurers be able to operate profitably? 2) Will consumers have a compelling reason to choose privately run Medicare plans over the public program?

We just don’t know yet.

The growing role of private insurance in Medicare, briefly explained

Talk about “privatizing Medicare” often goes back to what conservative former House speaker Paul Ryan championed for many years: a plan that phased out Medicare and replaced it with a voucher-like program to buy private health insurance — essentially giving seniors fewer resources to cover their care. But Medicare is extremely popular, and Republican’s abandoned that idea.

Of course, that’s not what Harris is proposing. That’s why Sanders’s language here about Harris’s plan is particularly inflammatory. But the reality with Medicare today is that Democratic and Republican policies over several decades have allowed private insurance to flourish under Medicare.

Harris wants to keep the existing Medicare structure. Since the 1970s, Americans in Medicare have been able to enroll in private health plans — both HMOs and PPOs — instead of the original Medicare program. These private plans operate differently than traditional Medicare. The government pays the private Medicare Advantage plans a fixed fee per enrollee, whereas traditional Medicare is a pay-by-service system.

Medicare Advantage has been popular with both enrollees and for insurers. Currently, roughly a third of Medicare enrollees, or 22 million Americans, are on some kind of private plan. Enrollment in Medicare Advantage has nearly doubled over the last decade.

For seniors, the plans are allowed to offer more benefits than traditional Medicare does, like hearing, dental, and vision, and the premiums are typically lower than having to buy supplemental coverage for traditional Medicare. And for insurers, they’ve been profitable. They usually restrict the network of health care providers, have healthier enrollees, and have been found to engage in some fraudulent practices to inflate the payments from the government, like claiming enrollees are sicker than they actually are.

“This is pretty much a slow but significant change for the Medicare program, but not what people would think of when they think of Medicare. It’s looking more and more like a marketplace of private insurers,” Neuman said.

The question is a matter of priorities: Should the government be paying private insurance companies and help them reap profits when it could expand coverage and benefits through a public program? This year, payments to Medicare Advantage plans were basically the same as the cost of traditional Medicare. But there’s also research that shows enrollees in Medicare Advantage plans usually use fewer services and have less health care spending. That suggests that there’s a lot of fluff in the system, giving federal dollars to private insurers who are then turning a profit.

Harris says private insurance would be strongly regulated in her plan, but we just don’t know how

Harris says her plan will have guardrails on these private plans to ensure they’re not engaging in fraudulent practices or unnecessarily taking tax-payer dollars. Private insurers would have to have their plans certified under “stricter” guidelines, the plan says. We just don’t know what those stricter guidelines are yet. And without those details, it’s hard to tell whether this plan would continue to grow private insurance’s role in Medicare.

The plan cites one restriction: To qualify, the private plan would be “reimbursed less than what the Medicare plan will cost to operate,” which is clamping down on a payment system that’s really allowed for private insurers to flourish in Medicare. In other words, the federal government would pay the private plans less than it spends on the public option.

At the end of the day, Harris’s plan pits a private option against a public one. Legislation would determine exactly how much room the private plans would have to differentiate themselves from the public plan. The plan doesn’t have details around the extent of benefits the private plans would be able to offer — a major factor in why Medicare Advantage is currently so popular.

And that, for the Sanders camp, opens too much risk for a profit-centered industry to enter the health care system. It leads to another gripe the Sanders campaign has with the Harris plan: It’s phased in over 10 years, more than the length of a two-term presidency, and according to the Sanders team, that’s too much time for the big insurance industry to step in and take over.

For now, Harris’s plan is just the broad outlines of a health care system that would incorporate a vastly expanded public option with a private system. But it isn’t yet legislation. Her mission here is more political. This is a plan designed explicitly to address various interests and concerns in the health care debate, including the role of private insurance.