“A lot of Democrats doubt that he can be nominated and be successful,” Richard Schinnow, a 76-year-old retired community-college teacher in a Patagonia jacket and glasses, told me as we waited for Sanders to appear. “But I do think that’s changing.” Particularly with a field of Republican candidates that is “so weak and so weird,” he said, many Democrats believe the presidency is theirs no matter who they nominate—so why not go with their hearts?

Mason City, two hours north of Des Moines, has a population of less than 30,000, but the hall was packed to capacity, with more than 1,000 people sitting in chairs, standing next to the hall’s quaint storefronts (dry goods, menswear), and listening from the next room. They cheered Sarandon’s arguments and cheered louder when Sanders took the stage. It’s one thing to draw thousands of kids to a Vampire Weekend concert on a college campus, as Bernie would do a few days hence. It’s another to bring them out here.

Whether or not Sanders succeeds, his rise to near-parity with Clinton, supposedly his party’s most inevitable candidate in many years, vividly illustrates the central revelation of the 2016 election: the lurking anger and radicalism that now exists on both sides of the electorate. The 2016 campaign’s twin unexpected phenomena—the parallel rise of Sanders and Donald Trump, who currently command an eerily similar 37 and 36 percent of their parties’ national vote in poll averages—have taken by surprise the pundits and wise men and party establishments who fundamentally underestimated partisans’ desperate desire for extremes.

The Beltway looked at Sanders and saw a raging figure on the fringe—an anomaly. If Sanders pulls out a win on Monday, he will have proven yet again that what seemed far-out was actually the party mainstream.

Sanders’s supporters love to ridicule the notion that socialism is something scary. They embrace it—they’re glad he’s made it a word you can say in public again. “I’m also a socialist,” John Dallas, a goateed Mason City housepainter, told me matter-of-factly. “I mean, how’s that capitalism working out in the United States? It’s fine for the top one-tenth of 1 percent, but the other 90 percent of us aren’t doing so well.”

And so Sanders has exposed the left-wing ideals in the hearts of a substantial portion of Democrats, just as surely as Trump has illustrated liberals’ stereotypes about Republican nativism and xenophobia. A Democratic Party that strained for decades to position itself as moderate, and to ostracize its radical voices, has instead seen its long-suppressed liberal energy burst to the fore.

“I think he’s more radical than the other people we’ve had, and I like that about him,” Taylor Raska, a 28-year-old bartender with a nose ring, mismatched earrings, and lines of cursive writing tattooed on her arms, told me. An ardent environmentalist who’s tired of politicians, Raska believes the old system must be smashed for a new order to take its place. “Everything’s going to change!” she said, savoring the beautiful thought. “We are in this amazing period—it’s awesome to be a part of. Everything is changing!”