DES MOINES, Iowa—“There is a huge grassroots movement,” explained Jeremy Schafer, one of many people who traveled from California to support Sen. Bernie Sanders in Iowa. “People building infrastructure to support future progressive candidates.” He continued: “Bernie Sanders is building a foundation. Win or lose, we will be there to keep Hillary honest and the next person honest.”

The Vermont senator isn’t running to hold Hillary Clinton accountable—he’s running to win. And at his final event before Monday’s caucus—a packed rally of more than 1,000 (possibly 2,000) supporters in a modest arena at Grandview University in Des Moines—Sanders made that clear. “You want a radical idea? All right, here’s a radical idea,” said the socialist who has captured the hearts of millions of Democratic voters. “Together, we’re going to create an economy that works for all of us, not just the 1 percent.”

To wild cheers from a crowd of college students and union volunteers, he pledged that he would fight for his smorgasboard of social democracy: single-payer health insurance, paid family leave, new infrastructure, tax hikes on big corporations, a $15 minimum wage, and free tuition at public colleges and universities. He called for equal pay for women, pledged to end “institutional racism” in the criminal justice system, and denounced companies like Walmart for paying workers so little that they qualify for Medicaid and food stamps. “I say to the Walton family: Get off of welfare, pay your workers a living wage,” said Sanders.

But for as much as Sanders indicted the “political establishment” and pledged to fight “the billionaire class,” this wasn’t a jeremiad. Sanders knows his crowd and they know him. When he hits his applause lines—“This will be a government for the people, by the people, and of the people”—they chime in to finish. And when an eager teenager screams “I love you Bernie!,” he smiles, grateful and (I imagine) a little embarrassed.

In a Sunday interview with NBC’s Matt Lauer, Sanders announced his plan to fight this primary to the end. “I hope we win, but if we lose by two points, so what—we’re going to go to New Hampshire, then we’re going to go to South Carolina, then we’re going to go to Nevada,” he told the Today show anchor. “We are in this to the end.” Sanders is in it to win it, and that gets to the truth of California supporter Jeremy Schafer’s statement. Win or lose, Sanders will stand as a historic presence in the Democratic Party.

Whether it was the socialist left in the 1950s and ’60s, the New Left in the 1970s, or the labor left in the 1980s, Democrats have always kept their left flank at arms length. This became principle (or, for critics, pathology) in the late 1980s and 1990s, when centrist reformers marginalized the left in a drive to—in their narrative—save liberalism from itself. Led by President Bill Clinton, and backed by a phalanx of Democratic lawmakers, Democrats built ties to Wall Street, embraced the conservative “war on crime,” and reshaped the safety net, scrapping programs like Aid to Families With Dependent Children in favor of more limited, market-friendly alternatives.

For a generation of Democrats who cut their teeth in the age of white racial backlash, the Moral Majority, and Ronald Reagan—where “liberal” was a slur and conservatives controlled the zeitgeist—this was the only option. “The era of big government” had to be over if liberalism was going to survive.

For Sanders and others in the remnants of the old left, this wasn’t just wrong, it was ruinous. For them, Democrats would only flourish when they embraced the left. Twenty years after Bill Clinton won re-election on a centrist platform, and at the twilight of an administration that spurned the left as much as it embraced it, Sanders and his allies have all but confirmed their hypothesis. With uncomplicated language and simple sincerity, Sanders has rallied millions of Democrats under the banner of “democratic socialism”—a kind of neo–New Deal liberalism, set against Barack Obama and Hillary Clinton’s attempted synthesis of Great Society policies and Third Way politics—and moved “socialist” from the realm of epithet to legitimate label.

Win or lose, that counts. It’s the Democratic analogue to Reagan’s 1976 primary against Gerald Ford—a sign of the times and of the future. If Sanders wins Iowa, New Hampshire, and the nomination, then he’ll bring (or drag) the Democratic Party to the left. If he loses, then he’ll represent the largest faction in the party, with the power to hold a President Hillary Clinton accountable and even shape her administration, from appointments and nominations to regulatory policy.

With that said, the impact of Sanders goes beyond presidential politics. I am skeptical that any “political revolution” can change American politics in the short term. But if Sanders inspires supporters to delve deeper into Democratic Party politics, then it could change the long term. His supporters—his workers and volunteers and activists—are (potentially) the next generation of Democratic operatives, who will bring the lessons of this effort to future campaigns. And in the same way that Jesse Jackson opened the door to politicians like Barack Obama, Sanders may do the same for “democratic socialists.” Like the veterans of George McGovern or Howard Dean, the veterans of Bernie Sanders will change and shape the Democratic Party.

The Iowa caucus will make or break the Sanders campaign. Without a win, it’s hard to see his path to the nomination. But it means little for his legacy. Sanders is already a historic candidate—the first socialist in a century to build a genuine mass movement in American party politics. And whatever the Democratic Party is in the next 20 or 30 years, it will owe a great deal to Sanders and all the people—young or otherwise—who felt the Bern.

Read more of Slate’s coverage of the Democratic primary.