The thin blue line has suddenly become much thicker. The Democratic Party is the only thing that stands between the world and the triumph of autocracy in the United States. Only a month ago, it seemed like a thin and fraying thread. Last week in Chicago, it felt like an electric fence.

Donald Trump’s fans chant “Build the Wall.” Perhaps his enemies have just done just that – erected a sufficiently strong barrier along the border between democracy and authoritarianism.

Last week I was at the Democratic National Convention and covered it for the New York Review of Books. It was like diving into an ocean of euphoria. The massive United Center was shaking like it probably did when it was Michael Jordan’s home stadium or when U2 played there.

At times it was important to remember that this was not just a great game or a spectacular show. It was a key moment in the fight for democracy’s survival in the 21st century. The discrepancy between the almost unadulterated joy of the occasion and the immense seriousness of what was at stake was at times dizzying.

The energy was like a euphoria of respite. This party was paralyzed in the first half of a crucial election year. It sat quietly in the corner, reading the chronicle of a death foretold – the impending demise of the American republic.

Even though Trump openly used Nazi rhetoric about immigrants poisoning the bloodline, even though his allies publicized their plans to bomb women’s and workers’ rights across the board, build concentration camps for “illegal” immigrants, and replace the civil service with loyal apparatchiks, Democrats could not bring themselves to acknowledge the obvious. They could not say what Joe Biden finally said out loud on Monday night: “I’m too old to be president.”

But the ways of history are puzzling. If Biden hadn’t pushed for an unusually early debate with Trump in June, if Trump hadn’t accepted that challenge, if Biden’s collapse hadn’t been so total, what would Chicago have looked like last week? A gallery of stiff grins and brave faces, fake frenetic speakers yelling that Biden would win in November even though they and their audiences knew he wouldn’t.

But to the Democrats’ credit, they have provoked an equally large and opposite reaction to their own guilty inertia. The last month, after Biden agreed not to run again, was an extraordinary example of what it means to seize the opportunity. What I saw at the convention was a ruthlessly efficient display of purpose. Behind the relentless barrage of optimism, behind Kamala Harris’s beaming smile and Tim Walz’s avuncular charm, lies a fierce determination.

This is monomania. Nothing – and no one – can stand in the way of the one, holy and apostolic mission: to defeat Trump. There can be no deviations or distractions. At the convention it was clear that this is not an order from above. It is the almost universal mood.

Such universal unanimity is ecstatic, but not always pleasant to watch. It is, in effect, to define the horrors of Gaza as an unwelcome distraction. Protesters reading the names of dead children were kept far from the arena, where they could no longer be heard. Small protests from the congressional hall were silenced – not by thugs, but by other delegates.

No pro-Palestinian speakers were allowed on the main stage. Even more striking is that critics of Israel’s actions, such as Bernie Sanders and Alexandria Ocasio Cortez, kept their criticism to a minimum, expressing it only briefly and without too much deviation from the official line, which says that Gaza residents should be shown sympathy, but nothing more.

Ironically, the Democrats’ overwhelming unity has made them much more like Republicans, at least in this respect. They have nothing on Trump’s personality cult – Harris shared the spotlight with (and was, at least rhetorically, overshadowed by) stars like Michelle and Barack Obama and Oprah Winfrey. Trump would never do that.

But in Chicago, there was a parallel demonstration of unconditional loyalty. Tribal dynamics drive the Blues as much as the Reds. The troop rally was often literal – a parade of speakers waved their military documents and chants of “USA! USA! USA!”, both orchestrated and spontaneous, accompanied the performances each night.

And yet they must win. And they must do so with a black woman. That means they must triumph over the forces of racism and misogyny that have built up over centuries of American and human history.

Racism and misogyny have a strange place in today’s culture. Openly expressed, they alienate more voters than they mobilize. We’ve seen it before – Trump’s attempt to revive the birther strategy he tried to use against Obama against Harris (“I wonder if they knew where she was coming from”); JD Vance’s “childless cat lady” – has turned off swing voters.

But what about the less obvious underbelly of prejudice? How deep does it go? In Chicago, I got the feeling that no one really knows. Or where it lies. If it stays confined to existing Trump territory, it won’t matter in the election. But if it keeps enough white workers in Michigan or Wisconsin, for example, from heeding their unions’ call to vote for Harris, it could play a big role.

( Nancy Pelosi: the “Mother of Dragons” whose icy grip on the Democratic Party never meltsOpens in new window. )

So eyes on the prize. This is a brutal fight, and it will only get uglier as Trump’s panic becomes more hysterical. His only strategy will be to delegitimize Harris, not just as a person, but as a type of person. Her type cannot be American. Which of course means that most real Americans (who are not straight, white Christian men) are not American either.

With so many people at risk of being denied their right to belong, it would be nice if there were room for more openness. But in a defensive wall, gaps that let in light are also potentially deadly weak points.