In the latest volley of her multi-front January offensive against Bernie Sanders, Hillary Clinton is zeroing in on his single-payer health care plan.

The Clinton campaign launched an all-out assault on Wednesday, flooding cable television with surrogates to attack Sanders for not releasing details of his plan. The Clinton campaign also held a conference call with reporters to amp up the pressure on how the proposal would raise taxes.

After landing against Sanders blows on guns and electability, Clinton’s attack from the right on health care seems odd, at least on its face. Fully 81% of Democrats favor a Medicare-for-all plan, like the one Sanders is proposing, according to last month’s Kaiser Health poll.

But like so much in politics, Clinton’s fight is not what it seems. It’s not really about about health care, but about taxes and effectiveness – with a bank shot at Sanders’ electability.

Meanwhile, Sanders has responded by trying to move the debate back to the more favorable terrain of health care. He accused Clinton of adopting “Karl Rove tactics,” as spokesperson Michael Briggs put it, to oppose universal health care, and flip-flopping on the issue to boot.

Who wins this fight, if there is even a clear winner, will largely be determined on who wins the framing of it. Let’s dive in.

Close video Clinton: Sanders wants to dismantle Affordable Care Act Brian Fallon, national press secretary for the Hillary Clinton campaign, joins Thomas Roberts to discuss Clinton and Bernie Sanders growing closer in the polls. Brian Fallon, national press secretary for the Hillary Clinton campaign, joins Thomas Roberts to discuss Clinton and Bernie Sanders growing closer in the polls. share tweet email Embed

Team Clinton’s argument, in a nutshell, is that Sanders is afraid to release details of his single-payer health care plan because it contains a massive tax hike on the middle class that would exacerbate economic inequality.

Clinton has vowed not raise taxes on those who make less than $250,000 a year. Sanders, on the other hand, would need a “sweeping tax increase on the middle class” to fund his health care plan, Clinton spokesperson Brian Fallon said on the conference call Wednesday. “What he’s promising right off the bat are tax increases that would adversely impact the take home pay.”

Whether an argument on taxes convinces Democratic primary voters that Clinton cares more about economic inequality than Sanders remains to be seen, but she has a point on the missing details of his plan.

Sanders has been saying since at least July that he would roll out his Medicare-for-all plan “in the very near future,” but it has yet to come. In his capacity as a senator, he’s introduced legislation on the issue many times the past, but he has yet to explain how he would pay for it.

Sanders’ campaign released a fact sheet Wednesday explaining how the senator would pay for various programs, but a single-payer tax plan was not among them. Asked Tuesday night on CNN if he still planned on releasing details of his plans before the Iowa caucuses on Feb. 1, Sanders replied, “Absolutely. If I said we’re going to do it, that’s what we’re going to do.” But his campaign manager, Jeff Weaver, confirmed Wednesday that the campaign may miss that deadline.

“The Clinton campaign, unfortunately, does not get to dictate when we put things out,” Weaver told Chuck Todd on MSNBC’s “MTP Daily,” saying it would come “when it’s ready.”

With less than 20 days to go before the Iowa caucuses, Sanders has accumulated a stack of policy issues for which he has yet to provide details. And a series of promised major policy addresses on everything from foreign policy to immigration never materialized. That raises questions about his seriousness and ability to deliver progress, Clinton’s campaign suggests.

“I’ve been laying out very specific policies for months now and telling people how I would pay for them,” Clinton said on NBC’s “Today” show Wednesday. “I’m asking that Sen. Sanders does the same thing.”

Sanders, meanwhile, is fighting a battle on different turf. His campaign dug up an old tweet from Clinton campaign chairman John Podesta expressing support for single-payer health care. And they produced a note Clinton sent to Sanders in 1993 thanking him for his “commitment to real health care access for all.” Team Sanders says that while the plan will increase taxes, it will reduce health insurance premiums by even more and thus save money for Americans overall (something the Clinton campaign disputes).

“Now she’s attacking me because I support universal health care. In 2008, she was attacking Obama because Obama was attacking her because she was supporting universal health care,” Sanders said Wednesday on MSNBC. “I wish Hillary Clinton would tell the American people, does she support universal health care?”

Clinton’s campaign insists they’re not trying to attack single-payer health care – but it may be collateral damage. They won’t quite say she supports it. She “absolutely respects Democrats who support the principle of a single-payer system,” senior policy adviser Jake Sullivan said on Wednesday’s conference call.

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And as Sanders noted, when Obama attacked Clinton for wanting to raise taxes through an individual mandate to pay for her health care plan, Clinton fired back hard. “Since when do Democrats attack one another on universal health care?” she said in a video distributed by the Sanders campaign Wednesday. “This is wrong, and every Democrat should be outraged because this is the kind of attack that not only undermines core Democratic values, but gives aid and comfort to the very special interests and their allies in the Republican Party.”

There are plenty of good, progressive arguments Clinton could use against Sanders’ health care plan, but they’re not the ones team Clinton is emphasizing, at least for now,

If it comes down to whether Democratic primary voters care more about expanding health care or reducing taxes, the latter likely wins. Nearly one-in-five Democrats said health care was their top issue in a recent Washington Post/ABC News poll, compared to just 2 percent who said tax policy was most important.

But Clinton is also subtly evoking an electability argument against Sanders. By raising the issue of Sanders’ alleged tax hikes, team Clinton is reminding Democratic primary voters that Republicans will do the same, times infinity, if Sanders is the nominee. And while Clinton will probably never invoke the “S” word Republicans will have no qualms going after Sanders’ democratic socialism.

Still, for a candidate who has spent the entire campaign trying to convince voters she’s not a squishy moderate, attacking Sanders from the right on taxes may be a risky play.

“I’m not a political pundit, so I don’t know about the right versus the left,” Sullivan said when asked about it by MSNBC on the call.