Four years ago, when Eric Adams was elected mayor, New Yorkers were told that it marked the end of a progressive wave that had shaped national Democratic politics at least since the shock election of Donald Trump in 2016. Just five months ago, as Democrats reckoned with the meaning of a second loss to Trump, the refrain was similar: The party had been pulled too far left by its activist flank, which it needed to not just discipline but also perhaps disavow. At the time, Zohran Mamdani was registering just 1 percent support.

Now he has won a decisive primary victory by bringing a remarkably novel electorate to the polls. And a lesson of his shock victory is one we probably should have learned several times over the past decade: Politics are fluid, even quicksilver, and the just-so stories we tell ourselves about what is possible and what is not are almost always simplistic and in many cases just plain wrong.

New York is only one city, exceptional in many ways, and last week’s was just one election — a primary at that, featuring a front-runner burdened by laziness and a toxic past. And there are obvious reasons to think that the Mamdani playbook now being debated so furiously both by its admirers and by its detractors would not work in other parts of the country — at least, not in all of them. But Mamdani’s triumph is nevertheless, as I wrote a few weeks ago in anticipation, an extremely big deal, elevating an avowed leftist closer to a more consequential executive office than any has held in generations. And though Mamdani’s ascension comes with meaningful risks, it also throws open a whole new horizon of political possibility. Mamdani’s supporters are exhilarated by the fresh air. But the oxygen spent on him by his haters over the past week shows that they, too, think Mamdani’s win is a major national event.

Last month, I asked what stories we might tell about a Mamdani victory — for the left, for the city and indeed for the whole country. But election night delivered enough of an earthquake that a number of new and important story lines have emerged since — too many, I think, to organize in any way but as a grab bag of observations. Here are 10.

1. The American left has a new face, and New York City is now an extremely high-stakes progressive experiment.

These days, with American politics more and more nationalized, every candidate everywhere is, to some extent, required to participate in national debates and be subjected to national scrutiny (on cable news and social media as well as offline). Perhaps in another era or another city an election like this could be cauterized from the national landscape, allowing an experiment in one city to play out on its own terms. Not now.