With two weeks to go until the Iowa caucuses, the Democratic presidential race has finally kicked off in earnest, all thanks to a spat between Hillary Clinton and Bernie Sanders over the merits of single-payer health care.

Faced with the very real possibility that Sanders could win both the New Hampshire primary (where he's already leading) and the Iowa caucuses (where the two are neck and neck), the Clinton camp has decided to target Sanders's support for single-payer, arguing that it'd require massive middle-class tax increases (true), that Sanders hasn't been upfront about the details of his plan (debatable), and that single-payer could strip millions of Americans of their health insurance (not true at all).

This has provoked no small amount of consternation among left-of-center journalists and commentators. On the one hand, there's widespread agreement that Clinton is flagrantly mischaracterizing the nature of Sanders's proposals, and that some of her allies' critiques are wildly misleading. But Clinton's not the only single-payer skeptic out there, and the conflagration is opening up a debate about whether aiming for a single government-run health plan is really the best approach for liberals now that Obamacare is passed.

Here's the state of liberal debate on single-payer, and how it reflects on Sanders and Clinton's campaigns.

No, Bernie Sanders is not going to take your health care away

By far the strangest comment from Clinton and her allies was Chelsea Clinton's insistence that "Sen. Sanders wants to dismantle Obamacare, dismantle the CHIP program, dismantle Medicare, and dismantle private insurance," and that "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."

It's definitely true that Sanders wants to dismantle private insurance, but to claim that he wants to dismantle Obamacare, and especially to claim that he wants to dismantle Medicare, is disingenuous in the extreme. Sanders wants to make a Medicare-style program available to all Americans regardless of age, run either federally or at the state level. Describing that as "dismantling" Medicare is like accusing a supporter of same-sex marriage of wanting to "dismantle" civil unions: It's an expansion, not a rollback.

"If anything, a single-payer plan like the one Sanders envisions would result in more coverage than current arrangements would allow," the Huffington Post's Amanda Terkel and Jonathan Cohn point out. "The Affordable Care Act has produced a historic reduction in the number of people without coverage, but something like 9 or 10 percent of Americans remain uninsured." Sanders's 2013 single-payer bill — the American Health Security Act of 2013 — instructs states to enroll all Americans automatically, scooping up those 9 to 10 percent of Americans and getting them covered.

The most generous way to construe Chelsea Clinton's comments is to assume she's just talking about the political danger of reopening health care as an issue. That's what Jake Sullivan, Hillary Clinton's campaign senior policy adviser, is telling reporters: "I would underscore that to put this country back into that debate on health care is to put all of the progress that we’ve made on the Affordable Care Act [at risk]."

But even this is pretty disingenuous. Bernie Sanders voted for the Affordable Care Act. He strongly opposes its repeal. As president he would veto any attempts to repeal it, and given there isn't a possible world where Republicans get a veto-proof majority in both Houses and Bernie Sanders is elected president, that means that the coverage gains of the Affordable Care Act will definitely survive a Sanders presidency. He is not putting that at risk in the slightest.

Former top Obama adviser David Axelrod spoke for many liberals when he chided the Clintons on this point: "I don't think it was the right attack. Bernie Sanders is proposing single-payer, universal health care. You can hardly say he is trying to take health care away from anyone or retreat from Obamacare; he's trying to exceed it. And so it's not really an honest attack. And it's not something that they should have sent her out to do."

Attacks from Hillary herself have been less brazen, but still prompted rebukes. "[Sanders] wants to roll Medicare, Medicaid, the children's health insurance program, the Affordable Care Act program, and private health insurance into a national system and turn it over to the states to administer," she said in Ames, Iowa. "I think that would be a big problem." Clinton's partly right: It's true that the American Health Security Act of 2013 would run single-payer at a state level.

But Ryan Cooper at the Week reached out to the Sanders campaign, which clarified that if states refuse to set up single-payer systems or don't meet the requirement of a federal board setting standards, the federal government would take them over. That certainly doesn't seem like a system that states could use to reduce health access.

The Washington Post's Paul Waldman is a little more sympathetic to Clinton — "Does that mean that if Sanders’ bill became law, an unusually creative Republican governor couldn’t find some way to undermine it and deprive his constituents of coverage or benefits? Maybe, maybe not; it’s hard to predict" — but notes that Sanders's counterarguments to Clinton's fearmongering about renegade states are "perfectly reasonable."

Beyond these specific points, a lot of commentators were surprised and concerned, to say the least, about Clinton apparently rejecting the idea of expanding government health care programs to make them more universal. She's, in the words of Slate's Jim Newell, "dressing up standard right-wing arguments against socialized health insurance as from the left."

Given that the idea of single-payer is broadly popular among Democrats — a December poll found that 81 percent of Democrats support "Medicare for all" — and that single-payer advocates are very passionate and vocal in primaries, the sense is that Clinton's attack will almost certainly backfire.

But single-payer is not perfect

That said, plenty of liberal commentators are registering some discomfort with aspects of Sanders's approach. His lack of details beyond the 2013 bill has, in particular, come in for a lot of criticism.

Sanders campaign manager Jeff Weaver has said the campaign's official single-payer plan won't necessarily come out before the Iowa caucuses, despite Sanders repeatedly pledging to release it by then. "Sanders should insist on the release of his plan as soon as possible," Newell writes. "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."

Sanders's dawdling is widely seen as reflecting apprehension about proposing the kind of tax increases necessary to fund single-payer. As the Washington Post's Greg Sargent notes, a new Sanders ad this week seems to suggest that single-payer can be paid for by making Wall Street pay its "fair share." This fall, when HBO's Bill Maher insisted that single-payer couldn't be paid for merely by taxing "the people who I think your fans think you’re talking about, the people who own a yacht," Sanders protested, "Not true, not true."

Sanders ultimately conceded to MSNBC's Chris Hayes this week that most people will have to pay more in taxes, while arguing that they'd still pay less than they would've in premiums to private programs, but a formal plan would make him get way more specific about that:

Sanders is probably right, by the way, that net of taxes and premiums, most middle-class families would benefit. UMass Amherst economist Gerald Friedman analyzed HR 676, the dominant "Medicare for all" bill in Congress, and found that the bottom 95 percent of Americans by income would see income go up, taking both new taxes and reduced premiums into accounts. The bottom fifth would see income go up by nearly 20 percent. Only the richest 5 percent are left worse off on average (and man, they're left a ton worse off):

But getting from here to there would require raising taxes, and telling voters to trust that the lower health costs would make up for it. HR 676 adds a bunch of taxes on rich people — a 0.5 percent tax on stock trades; a 0.01 percent-per-year-to-maturity tax on transactions for bonds, swaps, and trades; a 6 percent surtax on income above $225,000; a new 6 percent tax on investment income — but it also imposes a 3 percent payroll tax on wages under $53,000 and a 6 percent tax on wages above that.

Sanders's own bill, the American Health Security Act of 2013, adds a 6.7 percent payroll tax and a new progressive income tax (2.2 percent for income under $200,000 for singles, with rates up to 5.2 percent for people making more than that), as well as a 5.4 percent surtax on the incomes of millionaires.

Single-payer requires taxes the middle class is going to pay, and that makes single-payer a hard sell politically, even if it benefits the middle class ultimately. As Vox's Sarah Kliff has explained, the large taxes on small employers and middle-class employees required by Vermont's proposed state-level single-payer plan led to the idea being nixed entirely.

"Single-payer proposals are often hit with misleading attacks that ignore the advantages that have made them so popular in much of the rest of the world," New York magazine's Ed Kilgore writes. "But let's don't imagine they are the political equivalent of a free lunch, either."

Making the math work also requires big savings from single-payer, and as Vox's Matt Yglesias notes, a lot of that savings is going to have to come from cutting pay to doctors. That's really, really hard politically above and beyond the basic difficulty of getting single-payer passed.

"If the political consensus did exist for enacting large, across-the-board cuts in doctors' fees and hospital charges, then there would be no need to shift to a single-payer system in order to accomplish the cuts," Yglesias writes. "In the absence of such a consensus, the switch to single-payer actually wouldn't save money, and the costs would become exorbitant."

The physician and writer Adam Gaffney disputes this, noting that single-payer could save about $375 billion annually just through more efficient administration. But Yglesias's core point, that every dollar not squeezed out of doctors needs to be squeezed out of workers in the form of higher payroll taxes, is hard to argue with.

Can't we all just get along?

On some level, this argument is all just academic. The Affordable Care Act is probably the most bare-bones version of universal health care that you could still call "universal" with a straight face, and it barely got through Congress, and then only after abortion coverage was compromised and the public option was stripped out.

And even then it only passed because Democrats had their largest Senate majority since the Carter administration due to a disastrous Republican war and a massive financial meltdown. Those aren't conditions that are going to repeat themselves anytime soon — or, at least, one shouldn't want those disasters to happen again.

All that means that neither a President Sanders nor a President Clinton is going to have any chance of passing all-out single-payer. But if Democrats get really lucky and retake the House — realistically in 2020, not 2016 — they could maybe get the next best thing through: the public option.

As the New Republic's Brian Beutler points out, the public option gets around many of Clinton's gripes with single-payer. It could be federal, so states couldn't muck with it. Hell, you could just let people buy into Medicare qua Medicare. And the public option actually saves money by driving down the cost of private plans, so no new taxes are required.

Theoretically, if a public option is really good, it becomes more and more popular until it squeezes out private competition and the US becomes a de facto single-payer system after a while. And, of course, Clinton supported the public option in her 2008 run, so it shouldn't be too hard for her to get back on board now.

Even this is probably a lot to expect the next Democratic president to pass. He or she is likely not going to get the House back, and the public option pissed off a number of moderate-to-conservative Democrats in 2009/2010 too. But it's arguably a more plausible path to single-payer than passing single-payer in one go. And both Sanders and Clinton should theoretically support it.

Of course, primary elections are about accentuating candidates' differences, not finding common ground, so one shouldn't expect the candidates to abandon their current arguments in favor of saying, "Well, we can all agree on a public option." But as a political strategy for Democrats as a whole, it makes a lot of sense.