In the coming decades, the Democratic party may see a serious growth spurt — and it’s in large part thanks to Bernie Sanders, and the young generation of voters who support him. According to a new Harvard poll, 18- to 29-year-old voters have become significantly more liberal in the past year — in fact, their preference for Democratic control of the White House has nearly doubled — and Sanders is the most popular candidate among that age group.

Throughout the current primary season, one thing has certainly been clear: Bernie Sanders has a strong hold on millennial voters. Since before the primaries even started, polls showed that young Democratic voters were “feeling the Bern,” and siding with the Vermont senator over the party’s frontrunner, former Secretary of State and First Lady Hillary Clinton. And throughout this election season, millennials have stood by Sanders, helping him win many states. Though a majority of 18- to 29-year-olds reject socialism (Sanders considers himself a “democratic socialist”), the group largely identifies with the senator’s anti-establishment message and how it relates to their increased frustrations over things like student debt and income inequality.

And though, after Clinton’s big New York win, it looks like Sanders may ultimately lose the battle for the Democratic presidential nomination this year, he is winning a bigger war for the political party. Sanders is strongly influencing the way millennials think about politics and the big issues, and thus helping to build a generation of left-leaning voters. “There is no question that there is a significant part of the electorate that he has woken up and is organizing,” Harvard Institute of Politics polling director John Della Volpe told The Washington Post.

According to the Harvard poll, there are more self-identified Democrats than Independents among young voters for the first time in five years, and support of “progressive ideology” has especially increased in the past year. And overall, Democrats have the highest approval in five years. “Millennials care deeply about their futures and in this election cycle they are laser-focused on issues like access to educational opportunity, women’s equality, and the economy,” Harvard Institute of Politics director Maggie Williams said in the poll report. “This survey reflects their passion, their worries, and most importantly, a growing awareness that their voices have power.”

These numbers are so important, not because millennials are turning up to polling places in throngs to place their votes (as The Washington Post pointed out, only 41% of 18- to 24-year-olds voted in the last presidential election), but because, as they age, they will be and will likely stick with the political beliefs that they’re forming now. Studies show that ages 14 to 24 are the most formative years when it comes to solidifying political preferences, and that few people change course after age 30. So the influence Sanders has on young voters now may not win him this election, but it could very likely strengthen the entire Democratic party in the years to come.

“He’s not moving a party to the left,” Della Volpe said. “He’s moving a generation to the left. Whether or not he’s winning or losing, it’s really that he’s impacting the way in which a generation — the largest generation in the history of America — thinks about politics.”

Related: Watch Out Hillary: Bernie Sanders Is Winning the Youth Vote