I spent some of the best years of my twenties as a graduate student at the University of Toronto, where I was able to access Canada’s single payer health care insurance. There is no question in my mind that such a system of universal health care should be the objective of progressives in the United States. The crucial debate, as far as I am concerned, is how we get to that objective, and how we get there as quickly as possible.

I have been struck today by how much of the argument I saw in the last few days before the Nevada caucuses, much of which was swirling around disagreements between the Bernie campaign and the Culinary Workers Union in Nevada, was based on a common misunderstanding of the dynamics of negotiations. It was one that I often confronted when I was a union leader involved in negotiating a contract.

The misunderstanding takes this basic form: we should always ask for maximalist demands, because the give and take of contract negotiations means when we end up in the middle, and the result will be more to our liking. Conversely, the logic goes, if we demand something short of the maximum position, the final result will be less to our liking.

Alexandria Ocasio-Cortez used this logic, in which she said that the worst-case scenario of a maximalist demand for single payer health care now is that we would end up with a public option. In fact, we could well end up with less, even with a Democratic President and a Democratic Congress.

Here’s why.

The notion that making maximalist demands will end up with a result that is more to our liking ignores the role of power and leverage in a negotiating and bargaining process. Instead, it treats it as if it were a chess game or a card game in which the parties were fundamentally equal. But that is never the case in contract or political negotiations. One is always bargaining from positions of strength and/or weakness. Most often, your position is a combination of strengths on some questions, and weaknesses on others.

That is why the union I have been part of, the American Federation of Teachers, is always trying to build its power so that it can enter negotiations with greater leverage. A successful strike, for example, is a way to build leverage. But when all is said and done, what we are able to achieve at a bargaining table is based on our strength, and how adeptly we employ that strength.

The same is true of political negotiations.

In the most optimistic scenarios for the 2020 elections, Democrats will win a 53 or 54 seat majority in the Senate. No one, not even the most Pollyannish of observers, believe that Democrats could win a 60+ majority in the Senate, which would be a minimum requirement to win a vote on health care if the filibuster remains intact, as Bernie has said he wants to do. Elizabeth Warren would do away with a filibuster, although it is far from clear that there are enough Democrats supporting her position to accomplish that; she would not have Bernie’s vote, for example, if he held to his current position. Even without a filibuster, there are several Democratic Senators who have already indicated that they would oppose a single payer plan.

I know that some, including Sanders, argue that a social movement will somehow change all those calculations, and render the impossible possible. But there is really no precedent or basis for this in recent history, or in any conceivable balance of power Democrats would have after election day in November 2020. Arguments that reference the power of social movements in grand and abstract ways, without any sense of the actual points of leverage a social movement could possess and wield, make the social movement into a magical totem. The slogan of the 1968 protests in France — “be realistic, demand the impossible” — makes for nice poetry, but very poor politics.

In other words, when one demands a maximalist position that can’t be achieved — and moreover, that the other side knows can’t be achieved — one reveals the weaknesses of a negotiating position.

People often tell me that the threat of single payer will force the health insurance industry to concede to a public option. But if that is an empty threat, and if the industry knows that we can’t achieve it, they will be only too happy to have us spin our wheels demanding it, without conceding one inch on a public option.

In fact, when you are not fighting for a realizable demand, you are squandering the leverage that you do have. When your negotiating stance overextends your actual leverage to achieve your demands, you end up with less, not more — and conceivably with nothing.

Moreover, demands are implicit promises to your base. They know you won’t achieve all of it, but they expect you to come pretty damn close.

When you make a maximalist demand you can’t possibly achieve, and fall far short, you can only end up disappointing and disillusioning your base. You don’t have to spend very much time on social media, to find all manner of Bernie-stans who sincerely believe that his election would bring single payer health insurance, in part because they are new to politics.

A smart negotiations stance builds as much leverage as possible, and carefully calibrates demands to actual leverage.

Having presented the logic for my heresy, let me state it plainly:

It would be far better to have a demand that seeks to win the winnable, and institute the strongest possible public option in 2021 , given the leverage we will hold if we have Democratic majorities in the House and the Senate and a Democratic president.

We could focus, for example, on a public option plus, that was an opt out, rather than an opt in — which would leave the public option much stronger, but without giving our opponents the ability to claim that we were taking away choice, including from Democratic candidates who should know better.

Such a public option would, like Social Security and the ACA, become a floor that Republicans could not successfully repeal. It would provide a platform from which a full single payer could be launched in the future. It would also make it possible to address in an intelligent way the issues of transition, which are quite real and not resolved by the aspirational language currently in the “damn bill” Bernie wrote, absent any convincing plan of implementation. We should not forget that the ACA was almost killed at birth by all of the implementation issues and over-promising, and do our best to avoid it.

To put all of my cards on the table: this is why I think that the plan Elizabeth Warren laid out for a transition to single payer, which would start with demanding what will be possible in 2021 — a strong public option plus, and using that as a floor to win full single payer down the road, when we have the leverage in Congress and the White House — is the way to go, and why I think Bernie Sanders should embrace it.

The attacks on Warren’s plan as a “betrayal” of Medicare for All actually “betray” a misunderstanding by those who make them of how you win gains in a negotiations and bargaining process.

Leo Casey is Executive Director of the Albert Shanker Institute, Washington, DC.