At Sunday’s Democratic Presidential debate, Bernie Sanders called for a “political revolution” and criticized Hillary Clinton for accepting speaking fees from Goldman Sachs. PHOTOGRAPH BY PATRICK T. FALLON / BLOOMBERG VIA GETTY

As Eugene McCarthy and George McGovern demonstrated in 1968 and 1972, respectively, the sweet spot in the Democratic electoral calendar for an insurgent liberal-leftist campaign is often right about now: those weeks in the deep midwinter of an election year when the nation’s eyes turn to Iowa and New Hampshire, two states with a populist streak. Senator Bernie Sanders, of Vermont, is running strongly in both places. At Sunday night’s television debate, which was held in South Carolina, he was inevitably the center of attention. He made the most of it.

It wouldn’t be quite accurate to say that Sanders won or lost the debate. In tone, if not always in substance, the two brands of politics that he and Hillary Clinton are hawking to voters are so different as to be virtually incommensurable. The former Secretary of State is offering experience, electability, and toughness. Sanders is offering fire and brimstone. Both did a good job of laying out their wares, although, given the gulf between them, it is hard to see how mere presentation could be the decisive factor in the primary process. The key issues are how far to the left Democratic voters have moved in the past few years, and just how alienated from the party establishment they are. That is what will determine how far Sanders can go.

Under pressure to avoid a repeat of her defeat in the 2008 Iowa caucus, Clinton persisted in her recent attacks on Sanders’s record on gun control, and on his proposal to establish a single-payer health-care system. Sanders described Clinton’s characterization of his record on gun issues as “disingenuous,” and dismissed as “nonsense” her suggestion that his health-care reforms would undermine Obamacare. In presenting his own platform, he didn’t say much that was new: that is his great strength. Like Donald Trump, he always delivers the same straightforward and distinctive message—one that, for many months now, has been drawing huge crowds of Democrats and independent voters to events across the country. “What the American people understand is we have an economy that’s rigged,” he declared in his opening statement. “This campaign is about a political revolution to not only elect a President but to transform this country.”

What was different from previous debates was Sanders’s eagerness to go on the offensive against Clinton, and particularly to highlight her most vulnerable area: her ties to the Wall Street plutocracy. Twice, Sanders mentioned that she has received generous speaking fees from Goldman Sachs. The NBC anchor Lester Holt, the co-moderator of the debate, asked Sanders how his approach to bank regulation would differ from Clinton’s. “Well, the first difference is I don’t take money from big banks,” Sanders replied. “I don’t get personal speaking fees from Goldman Sachs.” Sanders’s second jab came after Clinton claimed that she had the toughest, most comprehensive plan to regulate Wall Street. This time, Sanders added a dollar figure, pointing out that Clinton “received over six hundred thousand dollars in speaking fees from Goldman Sachs in one year.”

In the past, Clinton has sought to defend her paid speaking appearances by explaining that she donated many of the fees she received to the Clinton Foundation, the family-run philanthropic organization that helps direct money to fight hunger, poverty, and disease. On this occasion, she tried a couple of different tacks. The first time Sanders brought up the subject, she accused him of disloyalty to President Obama, saying that the Vermont senator had called the President weak and criticized him for accepting donations from Wall Street when Obama had led the country out of the recession. It wasn’t clear what that had to do with the issue at hand.

When Sanders brought up the speaking fees for a second time, Clinton pointed out that he was the only one on the stage who had voted, some years ago, for a piece of legislation that deregulated some types of derivatives. This “we are all sinners” defense didn’t seem very convincing, either. Sanders, if he’d had his wits about him during this exchange, could have pointed out that it was Clinton’s husband who signed the offending law, the Commodity Futures Modernization Act of 2000. Instead, he confined himself to saying that anybody could check his record on fighting Wall Street deregulation and Wall Street lobbyists.

Presumably, many of Sanders’s supporters, particularly the young ones, have already done this. They will have discovered that he has been saying many of the same things for thirty years. To the progressive wing of the Democratic Party, and to the many independents who are flocking to him in Iowa and New Hampshire, it is Sanders’s history as a critic of Wall Street, and his eagerness to rail against a corrupt political system, that are the keys to his appeal. So is his sheer orneriness, which betokens a certain authenticity and unwillingness to abide by political convention, such as the one that says that, in American politics, being labelled a socialist is a death sentence.

At one point, he interrupted a question from Holt to say, “We have to make Congress respond to the needs of the people, not big money.” “Senator Sanders,” Holt went on, “let me continue. You call yourself a democratic socialist . . . ” Sanders interrupted again—this time to say, “I do.” Holt persisted, and eventually got in his question: “How will you win a general election labelling yourself a democratic socialist?”

From my living room, in Brooklyn, I could almost hear the folks at Clinton H.Q., which is about half a mile away, screaming at their screens: “He wouldn’t win! He’d lose fifty states!” But Sanders didn’t get flustered. “The Democratic Party needs major reform,” he said calmly, then went on. “Instead of being dependent on super PACs, what we need is to be dependent on small, individual campaign contributors. We need an agenda that speaks to the needs of working families and low-income people, not wealthy campaign contributors.” After a brief interjection from Holt, Sanders continued. “I am very proud that, in this campaign, we have seen an enormous amount of excitement from young people, from working people. We have received more individual contributions than any candidate in the history of this country up to this point,” he said.

I looked up that claim, and it’s a fact. By mid-December, the Sanders campaign had received 2.3 million individual campaign contributions. According to an article in the Huffington Post, that is more contributions than President Obama had received by the same time in 2011.

To be sure, Sanders is still a long, long way from winning the nomination. On Sunday, a new NBC News/Wall Street Journal poll showed him trailing Clinton by twenty-five percentage points at the national level. (Perhaps this survey exaggerated Clinton’s lead—other national polls have showed the race tightening up—but it is still substantial.) Even if Sanders were to come out ahead in Iowa and New Hampshire, he would face a monumental task once the contest moved on to bigger, more populous states with bigger minority populations.

For now, though, Sanders is in his element, and, as always, he is on message. “We’ve got to get rid of super PACs; we’ve got to get rid of Citizens United,” he said in his closing statement. “And what we’ve got to do is create a political revolution which revitalizes American democracy; which brings millions of young people and working people into the political process. To say loudly and clearly that the government of the United States of America belongs to all of us, and not just a handful of wealthy campaign contributors.”