Democratic presidential candidate Kamala D. Harris (Robert F. Bukaty/AP)
Opinion writer

The most important policy issue in the Democratic presidential primary campaign is health care, and the primary divide between candidates comes down to this: Should we add some kind of public option, where anyone who wants to can buy into Medicare itself or a program similar to it (what I like to call Medicare-for-anyone), or should we go all the way to Medicare-for-all, a single-payer system?

There are both policy and political disagreements surrounding this question, and while I’ve discussed the policy before (and will again), for the moment I want to focus on the politics. In particular, I want to point to this new ad:

They’ve even got an ad in Spanish making the same argument.

You may be asking, Who is the Partnership for America’s Health Care Future? Just a bunch of reg’lar folks like we see in the ad, people who are concerned about America’s health-care future?

Well, no. It’s a coalition of pretty much all the industry groups that have an interest in keeping the current health-care system in place with as little change as possible — and certainly no change that could cut into their profits.

Included in that coalition are the health insurance companies, the hospitals, the pharmaceutical companies and a bunch of other groups that like things just the way they are, thank you very much. As the ad makes clear, those interest groups are going to fight just as hard against Medicare-for-anyone as they will against Medicare-for-all.

The opposition of industry is far from the only factor to account for when considering the political prospects of various health-care reform proposals, but it’s a key one. If they see this as a truly existential fight — and for the insurers in particular, it could well be — they will spare no expense in lobbying and PR to strangle it. Health insurance companies make tens of billions of dollars in profit every year. You think they’ll hesitate to drop a few hundred million on killing reform if their survival is at stake?

I haven’t heard any of the presidential candidates address how they’ll deal with that onslaught as they’re trying to get their reform passed, though I suspect if you asked them, they’d just serve up some pablum like “We’ll just have to take our case to the American people …” Nevertheless, it has to be taken into account and planned for.

When Democrats set out on the long journey that culminated in passage of the Affordable Care Act in 2010, they decided that the only way it could be done was to co-opt the health industry by making them a bargain: We’ll get you a bunch of new customers because we’re expanding coverage, and in exchange you accept a new regulatory regime that does things like forbid you from denying coverage for people with preexisting conditions. Whatever you think about it from a policy perspective, co-optation succeeded politically, by the skin of its teeth.

But that kind of bargain just isn’t on the table this time around, because the reforms we’re contemplating are much more sweeping (even the ones being proposed by moderates such as Joe Biden). There’s nothing you could offer insurers that would make them accept Medicare-for-all, since one of its main justifications is that insurers are leeches who provide no added value and suck billions of dollars out of the system, so we need to get rid of them (or, in the case of a plan like that of Sen. Kamala D. Harris, restrict what they can offer so much that they will no longer be able to extract anything like the profits they make now).

As for Medicare-for-anyone, the health-care industry obviously thinks it’s a way station on the road to Medicare-for-all, so they fear it just as much. And they might be right. If a voluntary public plan is as appealing and affordable as liberals think it will be, over time people would choose it by the millions, and private insurance would wither away.

I’m sure that about now Medicare-for-all advocates are saying, “If industry is going to oppose half-measures just as fervently as they’ll oppose Medicare-for-all, why don’t we go all the way? Either way we just have to beat them, so why compromise on the policy before we start?” Which isn’t an unreasonable position to take, but there are other considerations to keep in mind.

The most important is that the public — at the moment anyway — looks much more favorably inclined toward a voluntary public option than Medicare-for-all. Support for the latter in polls depends a lot on how you ask the question, but it can be as high as 50 or 60 percent and as low as the 20s. Medicare-for-anyone, on the other hand, is far more popular, with clear majorities supporting it in pretty much every poll.

Of course, that’s before we have an intense debate about one or the other, full of lengthy argumentation, poignant personal stories and Republican demagoguery (stay tuned for Revenge of the Death Panels). We can only guess at how public opinion will evolve over the course of that debate, and how wavering members of Congress will react to what they think their constituents want and fear.

Unfortunately, we can’t run the experiment twice, once with Medicare-for-all and once with Medicare-for-anyone, to see which one can pass. We’ll only get one shot. No matter which course Democrats decide on when they have the chance, the fight is going to be intense.

Read more:

Helaine Olen: Medicare-for-all would help pay for long-term care. Why don’t more people know that?

Paul Waldman: Medicare-for-all faces its moment of truth

Charles Gaba: Despite what Sanders says, Harris may have the best claim to Medicare-for-all

Paul Waldman: Medicare just turned 54. Let’s remember what Republicans said about it.

Seema Verma: I’m the administrator of Medicaid and Medicare. A public option is a bad idea.