Bernie Sanders claimed a “virtual tie” with Hillary Clinton in the Iowa Democratic caucuses. Photograph by Joshua Lott / Getty

After a remarkable night in Iowa, one that served as a rebuke to Donald Trump and to the opinion pollsters, the Democratic Party was faced with the prospect of confronting a youthful and articulate Republican candidate come November: Senator Marco Rubio, who finished a strong third in the G.O.P. caucus, behind Ted Cruz and Trump. Before then, though, Democrats have some messy internal business to deal with: Bernie Sanders, promoting an American version of "people power," has confirmed his capture of the Party's under-forty wing, which means trouble for Hillary Clinton.

Strictly speaking, the Democratic caucus finished in a dead heat. In the early hours of Tuesday morning, with ninety-nine per cent of the precincts having reported, the delegate count was six hundred and sixty-five for Clinton and six hundred and sixty-two for Sanders. (For some reason, the Democrats release only their delegate counts, not the number of votes cast for each candidate.) In terms of percentages, it was 49.8 per cent to 49.6 per cent, which rounds up to fifty-fifty. Barring something unforeseen, Iowa’s forty-four delegates to the Democratic National Convention will be equally divided.

This result doesn’t mean that Clinton won’t win the nomination. Although she seems likely to lose in New Hampshire next week, she remains a strong over-all favorite: on betting sites, even today, to win twenty dollars on Hillary emerging as the Democratic candidate, you would have to bet a hundred dollars. But for Clinton to unite her party and galvanize it for what could be a tough fight in the fall, she needs to find some way to appeal to younger voters, who have fastened onto Sanders’s anti-establishment message.

The age gap between Clinton supporters and Sanders supporters was huge. According to the entrance polls, which wrongly predicted a Clinton victory, Sanders got eighty-six per cent of the Democratic vote in the seventeen-to-twenty-four age group, eighty-one per cent in the twenty-five-to-twenty-nine group, and sixty-five per cent in the thirty-to-thirty-nine age group. Clinton, by contrast, was largely reliant on the middle-aged and the elderly. Among forty-something voters, she won by five percentage points. Among the over-fifties, she won by more than twenty per cent.

When you are so heavily reliant on support from older voters, it is tricky to project yourself as the voice of the future. At about eleven-thirty, flanked by her husband and daughter, Clinton addressed a crowd of cheering supporters and said that she was breathing a big sigh of relief—presumably a reference to the fact that she didn’t lose the vote, as she did in 2008, when she came in third, behind Barack Obama and John Edwards. The television networks had been reporting that the Clinton campaign was claiming victory this time, but the candidate herself stopped short of saying so. Instead, she indicated that she is ready for what looks like a lengthy battle ahead. “I am excited about really getting into the debate with Senator Sanders about the best way forward to fight for us and America,” she said.

At eleven-forty-five, Sanders addressed his supporters, who were cheering even more wildly than Clinton’s crowd had been. “Iowa, thank you,” he began, his voice hoarse. “Nine months ago, we came to this beautiful state. We had no political organization, we had no money, we had no name recognition, and we were taking on the most powerful political organization in the United States of America. And, tonight, while the results are still not known, it looks like we are in a virtual tie.”

That history explains why Sanders emerged as the big winner of the night on the Democratic side. Not only has he pulled off a rags-to-riches story, he has done it on the basis of a message that is more radical than anything Presidential politics has seen in decades—a message that he repeats with such regularity and relentlessness that his stump speech has become familiar to many Americans.

As he looked ahead to carrying on the fight in New Hampshire, he used many of his favorite lines. “It is just too late for establishment politics and establishment economics.” “We do not represent the interests of the billionaire class, Wall Street, or corporate America. We don't want their money.” “The American people are saying no to a rigged economy.” “We are going to create an economy that works for working families, not just the billionaire class.”

In the face of such an onslaught of populist rhetoric and the promise of some equally populist policies, what can an establishment politician like Clinton do? If the entrance polls that showed her winning handily had proved accurate, she would have been able to dismiss Sanders as a fringe candidate whose appeal was restricted to New Englanders and white, college-educated liberals. Now she will have to soldier on through New Hampshire, seeking to pull off a surprise comeback victory there, as she did in 2008. And if she can’t quite manage that—the polls, for what they are worth, show Sanders well ahead in New Hampshire—she will hope to turn things around in Nevada, where a Democratic caucus will be held on February 20th, and in the South Carolina Democratic primary, a week later.

No doubt, the going for Sanders will get a lot tougher once the race moves to states with much larger numbers of non-white voters. On the basis of her last name, her organizational ties, and her personal appeal, Clinton’s advantage over Sanders among minority voters appears to be substantial. A few months ago, however, her lead in Iowa also seemed quite substantial. As time progressed, Sanders was able to eat into it and, eventually, to eliminate it.

Speaking on CNN as it got late, David Axelrod, President Obama’s former campaign manager, made an acute point. One of Hillary’s problems is that her campaign is largely about her—her experience, her electability, and her toughness. “I will keep doing what I have done my entire life,” she said in her non-victory speech. “I will keep standing up for you. I will keep fighting for you.” Sanders, on the other hand, rarely mentions himself in his speeches. His campaign is all about his message of taking America back from the billionaires. And, as Axelrod pointed out, it is often easier to inspire people, particularly young people, with an uplifting theme than with a résumé.

This, of course, was also the problem that Clinton faced in 2008, when Obama ran on a message of hope and the slogan “Yes, we can.” In recent weeks, the Clinton campaign’s response to Sanders and his promises of ambitious policy actions has sometimes seemed to be “No, we can’t.” In Iowa, at least, that didn’t prove to be a winning message.