By most accounts (including the one below), Bernie Sanders did well in last night’s debate in Charleston, South Carolina. He certainly didn’t lose and may even have won. He was slightly sharper and nimbler than he had been in earlier debates, despite being wrong-footed yet again on the issue of gun control. Hillary Clinton, the more polished debater, had some good moments too, but she often seemed complacent. Again and again, she tried to wrap herself in the mantle of President Obama. She’s no longer insisting, as she did until quite recently, that she isn’t running for Obama’s third term. On the contrary, she presented herself last night as the candidate who would protect his legacy, while Sanders managed to convey both his respect for that legacy and his determination to push beyond it. So far, this has not been a campaign season that favors defenders of the status quo, and that is precisely the role in which Hillary Clinton was bound to find herself. She’s a very adaptable politician—some would say too adaptable—but she never had a chance of running as an outsider. Now, with only two weeks left before the Iowa caucuses, Sanders has pulled even with Clinton in the polling there, while maintaining a slight lead in New Hampshire. Clinton still has a substantial lead in most national polls, but it is becoming less substantial every week, and Sanders is already polling much better than Clinton among young voters, including young women, and in match-ups with the leading GOP candidates, Donald Trump and Ted Cruz.

The leadership of the Democratic Party, which never took Sanders very seriously, is finally starting to worry. So are center-left pundits. In this morning’s New York Times, Paul Krugman takes a shot at Sanders’s single-payer health-care plan, while New York Magazine’s Jonathan Chait has a blog post titled “The Case against Bernie Sanders.” One gets the sense that Krugman is slightly more sympathetic than Chait to Sanders’s underlying ideology, but both argue that Sanders’s leftist platform is unrealistic in the current political environment and could even threaten the important gains made by meliorist liberals in the past eight years. Their criticism of Sanders is a version of the argument that the best is the enemy of the good—though Chait at least would probably add that those who really care about the details of public policy know that the pragmatic good is actually better than the ideological “best.” (Chait disapproves of ideology and believes that good liberals are immune to it.)

To their credit, both Krugman and Chait try to avoid condescending to Sanders and his supporters, but there is some unavoidable condescension in their claim that Sanders is naïve in imagining single-payer health care could ever get off the ground in the United States. The title of Krugman’s column, “Health Care Realities,” suggests that supporters of a single-payer system—or what Sanders often calls Medicare for all—are, well, not quite in touch with reality. Krugman reminds readers that it was all a Democratic Congress could do to push through Obamacare, which was modeled on proposals originally advanced by Republicans. Krugman acknowledges that Obamacare is a kludge—“a somewhat awkward, clumsy device with lots of moving parts”—and that “if we could start from scratch, many, perhaps most, health economists would recommend single-payer, a Medicare-type program covering everyone.” But since we can’t start from scratch, we must settle for what’s possible now, even if it’s imperfect and inelegant. The Affordable Care Act still needs all the support it can get in the face of continuing Republican efforts to repeal it. And besides, says Krugman, politics is about trade-offs and priorities: Democrats should concentrate their energy on other issues where there is both more room for improvement and more room for maneuver rather than wasting their time on “a quixotic attempt at a do-over.”

Chait agrees with Krugman, and expands on this line of critique to challenge most of Sanders’s agenda and to question its appeal. By calling for a “political revolution,” Chait argues, Sanders is making a promise he can’t keep.

Sanders offers the left-wing version of a hoary political fantasy: that a more pure candidate can rally the People into a righteous uprising that would unsettle the conventional laws of politics. Versions of this have circulated in both parties for years, having notably inspired the disastrous Goldwater and McGovern campaigns. The Republican Party may well fall for it again this year. Sanders’s version involves the mobilization of a mass grassroots volunteer army that can depose the special interests. “The major political, strategic difference I have with Obama is it’s too late to do anything inside the Beltway,” he told Andrew Prokop. “You gotta take your case to the American people, mobilize them, and organize them at the grassroots level in a way that we have never done before.” But Obama did organize passionate volunteers on a massive scale—far broader than anything Sanders has done—and tried to keep his volunteers engaged throughout his presidency. Why would Sanders’s grassroots campaign succeed where Obama’s far larger one failed?

I think it’s still too early to say how large Sanders’s grassroots campaign may yet become. But putting that point aside, I’d like to offer an answer to Chait’s question. Obama’s passionate volunteers were drawn to his personal charisma and to the general promise of change after eight years of George W. Bush. Of course, Obama ran with a set of detailed policy proposals, but it wasn’t his proposals that created most of the excitement around his candidacy; it was his image and his rhetoric. Sanders’s only charisma is a kind of anti-charisma. If Obama is the coolest president we’ve ever had, Sanders is one of the least cool presidential candidates in recent history. He knows this, it doesn’t bother him, and he pays voters the compliment of believing it won’t bother them either. Like Trump, Sanders is an anti-establishment candidate, but unlike Trump and a lot of right-wing populists, he does not run on his personality or promise miracles of leadership that will somehow overcome structural constraints on executive power. He is always reminding his supporters that he cannot do what needs to be done alone—no president can. It will require a new movement that motivates people who have become cynical about politics to organize and to vote. (A candidate whose top five contributors include four investment banks is unlikely to dispel such cynicism.) Sanders’s campaign really is all about his policies, and his policies—some (but not all) of them long-shots, many of them undeniably radical relative to those of his opponents—make his campaign far more audaciously hopeful than Obama’s 2008 campaign.

Chait describes Sanders’s politics as “fatalistic” and “despairing,” but this gets it exactly wrong. True, Sanders despairs of any significant progress being made before we change the way political campaigns are financed (his perseveration on this point has become a joke among the Beltway commentariat). But he offers voters the hope that, even after Citizens United, such change is still possible if enough of them care enough to vote for it. It is the other candidates who are “fatalistic” about the role of corporate money in politics, which is why, unlike Sanders, they are willing to accept huge amounts of it. That, they would argue, is just the way the game is played, and always will be. Sanders dares to hope it might one day be otherwise, and refuses to pretend it makes no difference one way or the other. So long as politicians can’t afford to run for office without the support of rich donors, their decisions will predictably reflect the preferences of their donors rather than those of the public. Political scientists have a word for that: oligarchy. This is the central fact of American politics today, and it is the focus of Sanders’s campaign. His dissatisfaction with this state of affairs does not amount to fatalism or despair. At least, that is not the way most voters have understood it; they have understood it as outrage or indignation. The challenge for the Sanders campaign is to get them to understand—and embrace it—as righteous indignation.

Chait shrewdly observes that the issues Sanders cares most about are not the ones a president, acting alone, can do much about.

Those areas in which a Democratic Executive branch has no power are those in which Sanders demands aggressive action, and the areas in which the Executive branch still has power now are precisely those in which Sanders has the least to say. The president retains full command of foreign affairs; can use executive authority to drive social policy change in areas like criminal justice and gender; and can, at least in theory, staff the judiciary. What the next president won’t accomplish is to increase taxes, expand social programs, or do anything to reduce inequality, given the House Republicans’ fanatically pro-inequality positions across the board. The next Democratic presidential term will be mostly defensive, a bulwark against the enactment of the radical Ryan plan. What little progress liberals can expect will be concentrated in the non-Sanders realm.

This is all true as far as it goes. But it fails to address two important points, one about the modern presidency and one about Hillary Clinton. Chait is right that, in functional terms, the most a Democratic president can hope to do in the immediate future is to serve as a bulwark against Republican lawmakers. But the presidency cannot be understood only in functional terms; it is also a bully pulpit. If the next president will not be able to change the tax code or curb Wall Street unilaterally, he or she will at least be better placed than any other politician to steer the nation’s political conversation toward subjects of real importance. That is what President Obama has done with gun control and immigration, and that is what Sanders would do with wealth and income inequality. If you believe, as many Democratic voters do, that those are the issues the country ought to be most focused on, then Sanders is your candidate. As Krugman might say, it is a question of priorities.

As for foreign policy, the area over which presidents retain "full command," former Secretary of State Hillary Clinton may know more about it than Senator Sanders does (though, as a member of the Senate Foreign Relations committee for fours years, he probably knows more about it than most pundits allow.) What voters are looking for in a Democratic presidential nominee, however, is somone who can be counted on not to lead them into another unnecessary war. And here Sanders has the clear advantage over his main rival. Clinton voted for our last unnecesssary war, the effects of which continue to afflict the Middle East. Sanders was one of the few who voted against it.

Which brings me to my main point about Hillary Clinton. If, as Krugman and now Chait have argued, what we need most in the White House is a dependable bulwark against Republican mischief, then we should be voting for a candidate whose record demonstrates consistent opposition to Republican policies. That candidate is Sanders, not Clinton, who has been all over the place on many issues. When her husband’s administration was working with both parties in Congress to deregulate Wall Street, she was in favor of deregulation. Now she promises to regulate everything, including shadow banking. Not very long ago, she supported the Trans-Pacific Partnership trade pact; now she opposes it. Clinton has also switched positions on gun control, immigration, and gay marriage. She is, as I mentioned before, very adaptable, not to say opportunistic. If Sanders’s campaign is less about personality than Obama’s was, it is also true that his appeal to voters who don’t trust Clinton has something to do with character. With most issues, including the ones that ought to matter most in this election, you know where Bernie stands: it’s where he’s stood all along. He may lack polish and aplomb, especially compared with Obama, but he’s solid. And that is exactly what you want in a bulwark.