In 2020 primary exit polls, most Democratic voters have said they support Medicare-for-all, but, as the Super Tuesday results showed, that stance hasn't always translated into votes for Sen. Bernie Sanders.

The exit polls from Super Tuesday repeated the trend we had seen in the early states: a majority of primary voters say they would support replacing private insurance with a single government plan, as Sanders’s Medicare-for-all plan would do. The margins varied across the day’s states, with the more liberal places being more in favor and moderate ones being more evenly split, but the trend was consistent.

And yet, it was Joe Biden — not Sanders, who “wrote the damn bill” — who had the big night and saw his odds of winning the nomination increase dramatically. Throughout the 2020 primaries, Medicare-for-all has gotten more support from Democratic voters than Sanders himself has. What that discrepancy suggests is that while Democratic voters do like the idea, it is not the determining factor in their vote.

The thing is most Democratic voters like Medicare-for-all and the “public option” plan supported by Biden and other moderates. That’s made it difficult for Sanders to make the primary a referendum on his health care plan with the party’s left-leaning voters, despite his success in moving the idea of Medicare-for-all into the Democratic mainstream.

At the decisive moment, it looks like Democratic voters weren’t totally willing to bet on Medicare-for-all. Sanders has time to recover in the primary campaign, but Super Tuesday was a step back for the candidate. His signature issue didn’t carry him and, instead, it is the moderate Biden who is pulling ahead.

Support for Medicare-for-all didn’t translate into a big Super Tuesday for Bernie Sanders

This underlying trend has been visible since the voting started in Iowa last month, but it fully revealed itself on Super Tuesday. In the early states, Medicare-for-all polled well — it approached 60 percent in Iowa, New Hampshire, and Nevada — and yet Sanders fell well short of that share in the primary vote. In South Carolina, single-payer was slightly above even with voters, but Biden smashed Sanders for his first win of the campaign.

The Super Tuesday exit polls displayed Sanders’s problem: He beat Biden among voters who support Medicare-for-all, but Biden still picked up a decent chunk of those people — and the former vice president won easily with Democratic voters who prefer the public option. Exit polls aren’t a perfect metric, but the trend was consistent across the 14 states that voted on the primary’s biggest day.

From the ABC News/Washington Post exit polls, these were the averages across all of the Super Tuesday states:

For voters who said health care was their most important issue, Biden outperformed Sanders, 38 percent to 30 percent

Among voters who said they support replacing all private insurance with a single government plan for everyone, Sanders got 42 percent of the vote. But Biden still picked up 25 percent of these voters; Elizabeth Warren, another Medicare-for-all supporter who has said Democrats should start with a public option and then pass single-payer, was the choice for 15 percent of those voters

Among voters who said they opposed Medicare-for-all, Biden won by a huge margin: 49 percent to Sanders’s 11 percent

Health care has frequently defined the policy debate between the 2020 Democratic presidential candidates. Sanders calls Medicare-for-all a moral urgency, given America’s failures to provide universal coverage. He wants to create a new government health plan that would cover every American, with no out-of-pocket costs except small copays on prescription drugs. He has boasted repeatedly in the primary that he “wrote the damn bill” to achieve the single-payer dream.

Biden, on the other hand, has labeled Sanders’s plan as fiscally irresponsible and too disruptive for mainstream American voters. His proposal would create a new government plan that would cover uninsured people; it would also be available on the Obamacare marketplaces for people who buy their own insurance and those who get employer-sponsored coverage would have the option to join the plan if they choose.

Sanders and his supporters believe more incremental proposals are just half measures. They point out Biden’s public option plan, despite covering millions more people than the status quo, would still leave up to 10 million Americans without health insurance.

The moderates contend a more incremental plan is the only one that can pass a narrowly Democratic Senate anyway, if the party is so lucky as to win the Senate in 2020 in the first place. Round and round it goes.

It doesn’t look like Medicare-for-all is a decisive issue for a lot of Democratic voters

But the lesson from Super Tuesday is this: Most Democratic voters aren’t basing their vote on the nuances of the Medicare-for-all debate. Supporting single-payer isn’t stopping a crucial segment of Democratic voters from backing Biden.

Here are some more important numbers: According to last month’s Kaiser Family Foundation tracking poll, 62 percent of Democratic voters said they favored both single-payer Medicare-for-all and a public option. For the rest, 20 percent said they support only the public option, and just 12 percent said they back only Medicare-for-all.

When the Democrats who said they support both policies were forced to choose one, a narrow majority opted for the public option.

And because they don’t necessarily have a strong preference between what Sanders or Biden is proposing, Democrats don’t seem to be making health care the issue that decides how they will vote.

Instead, the buzzword of the whole 2020 campaign so far — “electability” — looks more important to them. Beating Trump trumps health care. From the February KFF survey:

This has been the tension throughout the Democratic primary, obscured somewhat by Sanders jumping out ahead in Iowa, New Hampshire, and Nevada. He has a core base of supporters for whom Medicare-for-all exemplifies everything they like about him, and his ideas are quite popular among Democrats broadly.

But not everybody is sold on Sanders as the right messenger against Trump. The data is mixed on whether Medicare-for-all would hurt or help Sanders against the president — it may just be a wash — but many Democratic voters believe (rightly or wrongly) Biden would be more viable than the Vermont senator.

And on health care, the public option would be arguably a safer bet with the broader electorate. About twice as many 2020 swing voters say that they support a public option compared to single-payer, according to the recent KFF poll.

But the same rule applies to those voters as applies to primary voters: A relatively small number say support for or opposition to Medicare-for-all would be determinative for their vote. Voters say health care is important to them, but they aren’t caught up in the details. Broad themes like lowering costs and universal coverage appear to resonate most with them.

Sanders has put Medicare-for-all squarely in the middle of America’s health care debate. Much of the Democratic Party’s base supports it. But it doesn’t look right now like the enthusiasm he’s created for the issue will alone be enough to carry him to the Democratic nomination — or the White House.