A half-hour before a Bernie Sanders rally on Saturday night in Iowa, a line snaked around the nearly 900-seat Ames City Auditorium, but no one else was being let in: The theater was full.

Inside, the Grammy-winning indie rock band Portugal. The Man was playing. Rows of people were assembled on risers behind the musicians, waving Bernie signs. Sanders fans, most of them young, crowded the aisles; The Iowa State Daily reported that 1,400 people had crammed into the auditorium, with another 400 in an overflow room. The air buzzed with the intoxicating collective energy unique to social movements on the rise.

Sanders has a reputation for focusing on class to the exclusion of all else; as David Frum put it in The Atlantic, “‘Left but not woke’ is the Bernie Sanders brand.” On the ground in Iowa, however, it is not the brand of his campaign. Sanders isn’t just running the most economically left campaign; he’s running the most unapologetically left campaign, period. And it’s surging, with Sanders leading in recent polls in both Iowa and New Hampshire.

It’s no longer far-fetched to think that he could be the Democratic nominee.

When the band was done, three Indigenous women took the stage to pay respects to the Native Americans forced off the land that became Iowa. The filmmaker Michael Moore came on and described Donald Trump as the endpoint of a country founded “on genocide and built on the backs of slaves.” (The next day, at a campaign stop in Perry, Moore called women’s underrepresentation in Congress a form of “gender apartheid.”) Alexandria Ocasio-Cortez spoke, saying, “I’m here because Senator Sanders has actually committed to breaking up ICE.”