Welcome to the campaign trail, Chelsea Clinton. Got anything on your mind? “Sen. Sanders wants to dismantle Obamacare, dismantle the CHIP program, dismantle Medicare, and dismantle private insurance,” she said in New Hampshire on Tuesday. “I worry if we give Republicans Democratic permission to do that, we’ll go back to an era—before we had the Affordable Care Act—that would strip millions and millions and millions of people off their health insurance.”

The Hillary Clinton presidential campaign is in serious danger of losing both Iowa and New Hampshire, and this dire—though by no means fatal—situation is reflected in its new, aggressive posture toward her challenger, Sen. Bernie Sanders.

Her attacks are largely coming on two fronts: Sanders’ dicey history on certain gun control votes and his support for single-payer health care. While her criticisms of the former come from the left, her assault on the latter comes from the right, and it homes directly on a long-sought policy idea treasured by Democratic voters. The arguments her campaign is using against single-payer health care are earning plenty of griping from progressives, who see this as proof that Clinton will only play nice with them until the precise second that turning on them becomes politically advantageous.

So why does the Clinton campaign now consider attacking single payer so politically advantageous? In short, it’s the not-unfounded belief that once voters—even Democrats—hear more about what the implementation of single payer would entail, they’ll get cold feet. Though the Sanders campaign might roll its eyes at the misleading nature of Clinton’s attacks, it should treat this as an opportunity to have that debate, since it needs to be had, and won, when it eventually is brought up against the Republicans who will make the exact scare arguments that Clinton is making now.

The Sanders plan that the Clinton campaign is attacking is a 2013 piece of single-payer, or “Medicare for all,” legislation that he introduced. The bill would have folded existing insurance programs into state-run single-payer systems, in which the government covers all medical costs, effectively eliminating the private insurance industry. It would have paid for the proposal, as I wrote when Clinton first started wielding this attack in the fall, by levying a “2.2 percent tax on individuals making up to $200,000 or couples making up to $250,000, and progressively increasing that rate to 5.2 percent for income beyond $600,000.” Sanders’ 2013 plan “also would have tacked an extra 6.7 percent payroll tax on the employer side, at least some”—or all—“of which employers would likely pass on to workers.”

The Clinton campaign approaches Sanders’ strategy through a clever-but-not-really tactic of dressing up standard right-wing arguments against socialized health insurance as from the left. Sanders’ 2013 plan would have only “dismantled” existing health insurance programs in the sense that it would roll them into a new one in which everyone has medical coverage. Saying that it would “dismantle Medicare” is a truly head-spinning way of describing a plan that would enroll everyone in Medicare. The plan would indeed have raised taxes by an effective 8.9 percent on most individuals, and higher for those at the top—but no one would be paying insurance premiums anymore. The idea is that public, universal health insurance works out cheaper on net since the government would have lower actuarial and administrative costs, more leverage to negotiate medical costs with providers, and no profit expectations to meet. As for the Clinton campaign’s talk about how Sanders’ single-payer plan would have put each state single-payer system in the hands of Republican governors who could reject them, Sanders’ policy director tells the Week that they would be like Obamacare’s individual exchanges: If a state doesn’t set one up, the federal government would do it for them. (The Sanders campaign may also change this structure in its supposedly forthcoming new plan.)

Clinton is a health policy wonk and fully understands these arguments, but she and her campaign are nevertheless describing the plan as one in which apparently no one has access to medical coverage anymore but does, just for the hell of it, pay an additional 9 percent in taxes. These talking points do not endear Clinton to progressives who were already inclined to believe that her otherwise leftward posture this primary has been a temporary pose and that she will do anything to win.

But instead of just griping about Clinton’s play, single-payer supporters should meet her challenge head on—because it is a challenge.

The most common refrain I’ve been hearing from progressives in the past 24 or so hours is that it is electorally insane for Clinton to be using this particular tack, since single payer is so universally popular among Democrats. A December 2015 tracking poll from the Kaiser Family Foundation, for example, shows that 81 percent of Democrats either strongly or somewhat favor “having a national health plan in which all Americans would get their insurance through an expanded, universal form of Medicare-for-all.” Support remains high, too, among independents and even Republicans.

The political trouble comes, and would come if ever there were a push from President Bernie Sanders, when you start filling out what an “expanded, universal form of Medicare-for-all” means. First, it does mean the “dismantling” of private insurance. A lot of people like their employer-sponsored health insurance plans, even if they’re not the most cost-effective means of health care financing. Part of why Obamacare is so convoluted yet incremental in effect is that it went out of its way not to mess with the employer-sponsored health insurance system out of political necessity. Second, everyone would have to see a tax hike. Though the savings in eliminated premiums might outweigh the increases in taxes, as well as make people’s lives a lot easier, the prospect of higher taxes is still one that would give many initial supporters second thoughts about moving forward. Consider what happened when Vermont tried to institute a single-payer system.

As PolitiFact wrote in a 2009 review of polling on single-payer health care, so much of these polls hinge on the wording, which indicates how malleable public opinion is on the issue. “Words matter. Drop in the words ‘like Medicare’ and some polls have found the public responds better. People generally like Medicare,” they wrote. “Call it universal health care run by the government, and you often do better than calling it ‘single-payer.’ And if you call it a ‘socialized’ system, well, you can guess the results.”

Or, as another expert described the politics of single payer in 2008:

You know, I have thought about this, as you might guess, for 15 years and I never seriously considered a single payer system. Obviously, I listened to arguments about its advantages and disadvantages, and many people who I have a great deal of respect for certainly think that it is the only way to go. But I said, as you quoted me, that we had to do what would appeal to and actually coincide with what the body politic will and political coalition building was. So I think if you look at most public opinion surveys, even from groups of people who you would think would be pretty positive towards single payer, Americans have a very skeptical attitude. They don’t really know that Medicare is a single payer system. They don’t really think about that. They think about these foreign countries that they hear all these stories about, whether they’re true or not, which they’re often not. And so talking about single payer really is a conversation ender for most Americans, because then they become very nervous about socialized medicine and all the rest of this. So I never really seriously considered it.

That was Hillary Clinton. And now it’s those very fear tactics she described there as the political impediment toward enacting single payer that she’s employing now.

As dispiriting as this may be for progressive single-payer advocates, it would be even more dispiriting to see the Sanders campaign waver. And the Clinton campaign has made a strong point, one that it emphasized repeatedly on a conference call with reporters Wednesday afternoon: The Sanders campaign is not being forthcoming with the release of its specific single-payer plan.

Sanders had pledged that he would release his plan, an update on the 2013 version, before the Iowa caucuses. Following Tuesday night’s State of the Union, he reiterated that he would “absolutely” release it beforehand. “If I said we’re going to do it,” he told CNN’s Dana Bash, “that’s what we’re going to do.” Earlier this week, though, Sanders campaign manager Jeff Weaver said he didn’t have a “date” for its release and added, “not necessarily before the caucuses.” Weaver, CNN now reports, “stood by his comments on Wednesday, stating that the campaign does not yet have a date for when to release the Medicare-for-all plan.” It sounds like Sanders’ advisers are worried about the sticker shock of the plan, any honest version of which would include middle-class tax hikes.

Sanders should insist on the release of his plan as soon as possible. If his advisers are concerned about the negative short-term politics that would follow the release of the plan, they should also consider the negative short-term politics that come with them appearing to hide something and the Clinton campaign slamming them around the clock.

More importantly, if the single-payer movement is ever going to be successful, it requires honest and fair accounting about what implementing a single-payer system would entail. Yes, there would be tax hikes. Yes, employer-sponsored coverage would be a thing of the past. Yes, it would cost trillions of dollars over a decade. But then there are the many benefits.

If it wasn’t going to be Clinton making the misleading arguments against single payer, it was going to be Republicans. Sanders should welcome Clinton’s arguments and fight them as clearly and honestly as he can. If he can do so, and win, he will have done a stronger service for single-payer advocates and the ideals of democratic socialism than Clinton did a disservice.