On Monday night, Sen. Kamala D. Harris — whose presidential campaign rollout is going extremely well, you have to admit — did a town hall on CNN, answering all kinds of questions from a studio audience. At one point, someone asked about her position on health care and she said that she supports “Medicare-for-all,” then talked in general terms about why health care has to be a right and not a privilege.

But as we know, candidates can mean different things when they say Medicare-for-all. Most importantly, they might mean something like Bernie Sanders’s true single-payer plan, in which there would be only one insurer and private insurance would essentially cease to exist, but they might also mean something that would better be termed Medicare Access For All, in which people could choose to keep their private insurance or buy into Medicare (or Medicaid). That’s an enormous difference, in both policy and political terms.

A year and a half ago, Harris signed on as a co-sponsor of Sanders’s plan, but it would be perfectly possible for her to have described that as a kind of opening bid, a way of making a statement of her intention to make health care a right while still holding out the option to come up with a different approach that satisfies the same goals. But host Jake Tapper, knowing that this is an important thing to clarify, asked her to get specific about her support for Sanders’s bill:

TAPPER: I believe it will totally eliminate private insurance. So for people out there who like their insurance, they don't get to keep it?
HARRIS: Listen, the idea is that everyone gets access to medical care. And you don’t have to go through the process of going through an insurance company, having them give you approval, going through the paperwork, all of the delay that may require. Who of us has not had that situation where you’ve got to wait for approval and the doctor says, “Well, I don’t know if your insurance company is going to cover this”? Let’s eliminate all of that, let’s move on.

There are many arguments in favor of single payer, and the idea that it would make for smoother and less bureaucratic interactions between patients and doctors is just one you could focus on (there would certainly still be paperwork, but doctors would have to deal with only one insurer instead of many different ones, which would it simpler in some ways). But the most notable thing is that Harris, who isn’t starting out this campaign as the most liberal of the candidates, is putting her stake on the left side of this issue.

Presumably, at some point she’ll come out with her own specific plan, even if she has already endorsed Sanders’s. She hasn’t gone into too much in the way of specifics, though she has talked and written about how her mother’s illness and death shaped her views on the problems of the current system. But having taken and now reiterated the single-payer position, she won’t have much ability to move toward something different, especially with many Democratic primary voters seeing single payer as a litmus test.

Which raises an interesting question: What happens to Democratic candidates who want something not as sweeping as single payer? Are they going to be able to make the (necessarily more complicated) case for something different, or will all of them decide that it's just not worth it and they should get on the bandwagon?

I’ll confess my own bias on this question. For many years I advocated for single payer, but over time I came to the conclusion that we could achieve the same ends — universal coverage and lower costs — with an alternative that offered an easier path from where we are now. My own preference would be something like the hybrid system they have in France: a universal, basic program that covers everyone, plus the freedom to buy private supplemental insurance on top of that (which most people do). It’s not that different from Medicare, since 1 in 4 Medicare recipients purchase private Medigap policies.

Among the advantages are that we could scale up Medicaid to become the universal basic program and scale down existing private insurance to become the supplemental plans (and leave Medicare in place for older people). It wouldn’t be a simple transition, but it could be done gradually, and it would be a lot easier than just canceling every private policy entirely and moving everyone to Medicare.

President Barack Obama used to say that if we were starting from scratch, single payer would be the obvious way to go, but we aren’t. We have a system in place, employing millions of people and full of stakeholders, and as pathological as that system is, it has to be taken into account when designing reform. You can think the Affordable Care Act was way too modest about the solution but still acknowledge that he was right about the challenge.

If you gave Harris or other Democrats truth serum, I suspect they’d say that while single payer would be extraordinarily difficult to achieve, if nothing else it’s a good place to start the negotiation. If we begin there and then land on a hybrid system, that’d be more than fine with them. But one of the things recent history has taught us is that people fear change even if what you’re offering them is better than what they have now.

That’s a big reason voluntary plans, which you can buy into if you want, have a great deal of appeal. And the trouble with single payer as a political matter is that when Republicans say “Democrats want to take away your health insurance and put you on a big government plan!” — which they’ll say no matter what Democrats propose — they’ll pretty much be right, even if the big government plan will work out well for everyone.

So the question we’re left with is, what kind of health-care debate is the 2020 primary contest going to produce? If all the candidates just say, “Yep, Medicare-for-all is where it’s at,” that’ll be too bad. Not because it will make the nominee vulnerable to GOP attacks (after all, Republicans have zero credibility on the issue), or because single payer doesn’t have a lot to commend it, but because it means we’ll lose our best chance to really bore down on the strengths and weaknesses of the alternatives. But maybe I’m hoping for too much.