Last night the Democratic candidates for president held a debate in Charleston, S.C., and with all due respect to Martin O’Malley, I want to focus on what in the past week or two has become the main point of contention between Hillary Clinton and Bernie Sanders: health care. There are some disputes in the presidential campaign that involve tiny differences that the candidates portray as yawning chasms — see, for instance, Marco Rubio and Ted Cruz arguing about who hates “amnesty” for undocumented immigrants more — but this really is a major difference between two leading contenders. They disagree vehemently about it, and in a way, they’re both right.

The essence of the divide is this: Clinton wants to make relatively modest changes to the Affordable Care Act to fix specific problems with the health-care system, while Sanders supports remaking the system by moving to a single-payer plan similar to what every other industrialized country uses. This issue is an almost perfect microcosm of their entire campaigns, and it was clearly displayed in the debate, with Clinton talking about the value of incremental change and the need to be pragmatic and realistic, while Sanders offered a sweeping vision of revolutionary change.

“We finally have a path to universal health care,” Clinton said in explaining her opposition to Sanders’s single-payer plan. “We have accomplished so much already. I do not to want see the Republicans repeal it, and I don’t to want see us start over again with a contentious debate. I want us to defend and build on the Affordable Care Act and improve it.”

Sanders, on the other hand, spoke to Democratic heroes and liberal values: “What a Medicare-for-all program does is finally provide in this country health care for every man, woman and child as a right. Now, the truth is, that Frank Delano Roosevelt, Harry Truman, do you know what they believed in? They believed that health care should be available to all of our people.”

Clinton’s response was essentially that a bird in the hand is worth two in the bush — she cited the concrete improvements in people’s lives that the ACA produced and warned against the risk of restarting a huge debate over health care. Then the two had an exchange that brought their differing perspectives into sharp relief:

SANDERS: Do you know why we can’t do what every other country — major country on Earth is doing? It’s because we have a campaign finance system that is corrupt, we have super PACs, we have the pharmaceutical industry pouring hundreds of millions of dollars into campaign contributions and lobbying, and the private insurance companies as well. What this is really about is not the rational way to go forward — it’s Medicare for all — it is whether we have the guts to stand up to the private insurance companies and all of their money, and the pharmaceutical industry. That’s what this debate should be about.
CLINTON: Well, as someone who — as someone who has a little bit of experience standing up to the health insurance industry, that spent, you know, many, many millions of dollars attacking me, and probably will so again, because of what I believe we can do building on the Affordable Care Act, I think it’s important to point out that there are a lot of reasons we have the health care system we have today.
I know how much money influences the political decision-making. That’s why I’m for huge campaign finance reform. However, we started a system that had private health insurance.
And even during the Affordable Care Act debate, there was an opportunity to vote for what was called the public option. In other words, people could buy in to Medicare, and even when the Democrats were in charge of the Congress, we couldn’t get the votes for that.
So, what I’m saying is really simple. This has been the fight of the Democratic Party for decades. We have the Affordable Care Act. Let’s make it work.

Back in 2007, Mark Schmitt observed that the argument between the Democratic candidates was about whose “theory of change” was right — less about the substance of what they wanted to do, which was almost identical, than about how to go about achieving it. The substantive differences between Clinton and Sanders are larger than they were between Clinton, Barack Obama and John Edwards, but they’re still arguing about the theory of change.

Clinton’s theory of change is practical, realistic and born of hard experience. But it’s also not particularly inspiring. It takes opposition from Republicans as a given and seeks to avoid direct confrontation with certain powerful interests. It’s essentially the same theory Obama operated on in 2009, when his administration set about to co-opt the insurance and pharmaceutical industries instead of fighting them. And it worked — after half a century of Democratic failure on health care, they passed sweeping reform.

Sanders’s theory of change starts from the unspoken presumption that the ACA was in its own way a failure, because it didn’t change the system enough — there are still people left out, and though costs have been reined in, we still spend far more than countries with single-payer systems, and always will as long as we have a system based in private insurance. The problem with Sanders’s theory, however, is that it’s vague on getting from where we are to where he wants to go. He talks about the need to “stand up” to special interests and create a “revolution,” but standing up isn’t a plan.

Lest any of my friends supporting Sanders call me a squish, I’d note that I’ve been touting the benefits of single payer for years. In various forms it has been tried and worked far better than our system in every other advanced country in the world. In places like France or Germany or Japan, everyone is covered, the quality of care is as good or better than what Americans get, and it costs dramatically less than our bloated, inefficient system. But — and it’s a big “but” — moving from our current system to a single-payer system would be an extremely complicated endeavor, both practically and politically. If you tried to do it all at once, the opposition from both Republicans and the affected industries would make the fights over Bill Clinton’s and Barack Obama’s health-care plans look like nap time at the preschool.

But that doesn’t mean Sanders’s ideas about health care should just be dismissed. It’s no accident that he’s getting the support of millions of idealistic Democrats. He’s a radical, in the traditional sense of the word as one who gets to the root of things.

A real primary debate needs the elements that both Sanders and Clinton provide: on one hand, a fundamental examination of what drives the system and a vision that speaks to the party’s essential values, and on the other hand, a realistic assessment of what the next president can accomplish. That’s why even though they have a profound disagreement on health care, both of them are right.