The fight over health care in the Democratic primaries took a turn for the nasty this week when former Vice President Joe Biden said that proponents of the idea were, like Republicans, intent on getting rid of the Affordable Care Act.

The primary target of the attack was rival presidential candidate Bernie Sanders , the independent senator from Vermont and longtime champion of Medicare for All . Sanders quickly responded, first through aides and then in a speech that basically accused Biden of lying, although he never mentioned the former vice president by name.

Sanders had reason to be livid. Back in 2009, Sanders had voted for the Affordable Care Act , passing up opportunities to hold the legislation hostage as more conservative Democrats had. In 2017, when President Donald Trump and Republicans were pushing repeal legislation, Sanders fought them as energetically and effectively as any member of the Democratic caucus.

Sanders did these things because he understood that Obamacare was an important step toward the goal he and most Democrats have always shared: guaranteeing access to health care for every American. And its why Sanders is now making the case for his Medicare for All legislation. He thinks its the quickest, surest way to reach that objective.

But the converse is also true. At least some Democrats skeptical about Medicare for All remain very passionate about universal coverage. They simply worry the Sanders legislation would be too disruptive, as policy, politics or both. At worst, they think, it could alienate voters whose would otherwise support less ambitious, but still significant reforms.

These arguments may or may not be correct. But they certainly deserve a serious hearing, especially because Medicare for All isnt just another idea on the campaign trail. Its got the endorsement of several Democratic presidential candidates, including fellow front-runners, Sens. Kamala Harris (D-Calif.) and Elizabeth Warren (D-Mass.), and its captured the imagination of the partys activist base.

Medicare for All has been getting attention and generating excitement in no small part because, even with the Affordable Care Act in place, tens of millions of Americans are struggling with health care bills, sometimes with tragic consequences . But the case for Medicare for All specifically, as the best remedy to this problem, isnt as simple as proponents frequently make it seem.

What Biden Said, And Didnt Say, About Medicare For All

Bidens statements didnt come out of nowhere. Mondays remarks came as he was rolling out his own health care plan, which, among other things, would bolster the Affordable Care Act by making its financial assistance more generous and available to more people.

Bidens plan also has a public option. Specifically, it would create a new, government-run insurance plan that would be available to anybody who wanted to enroll in it. Critically, this new plan would be open to low-income people residing in states like Florida, Georgia and Texas where officials have refused to participate in the Affordable Care Acts Medicaid expansion.

Bidens approach would almost certainly make health care more affordable for millions. The new financial assistance, in particular, would make private insurance a lot more affordable to people who buy coverage on their own and who, because of the Affordable Care Acts more limited subsidies, struggle to cover premiums or out-of-pocket costs.

By the standards of past Democratic campaigns, Bidens proposal is ambitious and progressive. It feels timid only because Sanders and other Democrats are touting the more ambitious and more progressive Medicare for All an idea that, Biden says, would be too disruptive to existing insurance arrangements (since everybody would give up their existing insurance) and to the health care system more generally (since government would start paying everybodys bills).

But in making this case, Biden drew that toxic and misleading analogy to Republicans. I knew the Republicans would do everything in their power to try and repeal Obamacare, Biden said in an email to supporters. But Im surprised that so many Democrats are running on getting rid of it. Biden also made a point of addressing seniors specifically, warning darkly that the transition from existing Medicare to Medicare for All might leave them unable to get critical, life-saving treatments.

Every second counts. Its not about a year, its about the day, the week, the month, the next six months, Biden said, recalling his own experience watching loved ones go through terminal illness. The truth of the matter is, its likely to be a bumpy ride getting to where were going.

What Sanders Said, And Didnt Say, About His Critics

As Sanders and his aides pointed out, the benefits package under his plan would be considerably more generous than what exists under traditional Medicare. Currently, high out-of-pocket expenses cause most seniors to sign up for some kind of supplemental or alternative coverage , whether its private Medi-gap or Medicare Advantage plans or, if they qualify, Medicaid.

Despite what youre hearing about Medicare for seniors being weakened, the truth is exactly the opposite, Sanders said on Wednesday. It will be strengthened.

He also addressed head-on the worries about disruption. Sanders has always been forthright that his plan would mean eliminating existing private insurance, including employer-sponsored coverage, and that it would require people to pay the equivalent of a tax rather than premiums. On Monday, he mocked the idea that Americans would be upset about the shift, when what they really care about is keeping their doctors and hospitals and keeping their costs under control.

My Republican friends and some others seem to think that the American people hate paying taxes but they just love paying insurance premiums, Sanders said.

The insurance premium is here, what a wonderful day! Oh, wow! he joked. Lets celebrate! Hey!

And then, turning more serious, he noted that employer coverage isnt nearly as stable as defenders make it out to be, with insurers constantly changing provider networks, employers constantly switching carriers, and workers constantly losing employment altogether.

When our opponents talk about destabilization of the current system, they forget to tell you that the current system is already disrupting and destabilizing millions of peoples lives.

All of this is absolutely true. But polls have shown that, in general, people who have coverage are satisfied with it. And support for Medicare for All schemes consistently falls when pollsters tell respondents that enrollment in the new plan would be mandatory, even for people who already have employer coverage.

One reason may be that public opinion about Medicare for All reflects not just feelings about their existing insurance but also feelings about the alternative, especially in an era when faith in government remains, by historical standards , relatively low.

Plus there are bound to be Americans, maybe quite a few of them, who simply assume that any change is bound to be a change for the worse. And as the Obamacare experience showed vividly, people unhappy about health care reforms can be a lot more vocal than those who are happy about them.

What This Means For The Health Care Debate

Public opinion isnt static and Sanders contends that skeptics will warm to Medicare for All when they see what a good deal it is financially. To prove his point, he cites studies showing that his bill would reduce health care spending and, as a consequence, most people would save money.

But the studies Sanders has in mind typically assume that providers of health care would see substantial reductions in their revenue over time. That wouldnt simply mean paying a lot less to drug companies and insurers, whom Sanders loves to attack. It would also mean paying a lot less to doctors and hospitals, whom Sanders loves to champion as heroes and whom he mentioned no less than a half dozen times on Wednesday as allies in his fight.

This could turn into a policy problem, because excessive cuts could cause genuine access problems, and its already a political problem, because doctors and hospitals have a lot of influence. A new, industry-funded group fighting Medicare for All includes among its members three of the nations most powerful provider groups: the American Medical Association, the American Hospital Association, and the Federation of American Hospitals.

Of course, these groups also oppose more incremental proposals like Bidens because they would still reduce provider revenue, albeit a lot more modestly. One argument in favor of promoting Medicare for All is that it moves the boundaries of the political debate, so that these less aggressive initiatives come to seem more reasonable by comparison, and perhaps easier to pass.

But even seemingly moderate legislation can be difficult to pass. The history of Democratic attempts at health care reform, which goes back nearly a century now, features a lot more more failure than success and its why even people who share the goal of universal coverage can come away with such different views on how to get there.

Biden knows this because, as he likes to remind voters, he was part of the last big health care battle and lived through the political fallout. A lot of what he said this week was unfair. But not all of it.