Young voters want Bernie Sanders to be the Democratic nominee for president. But they don’t seem to want to turn out for him or at least not in the numbers he needs to win.

The youngest voters in Michigan, those 18 to 29 years old, gave the vast majority of their votes to Sanders. But at 16% of the electorate, according to exit polling, they were overwhelmed by the oldest voters, who were 20% of the electorate and gave most of their votes to Joe Biden. The next youngest voters (aged 30 to 44) also backed Sanders, 52% to 42%. But they were swamped, in turn, by the next oldest voters (aged 45 to 64) who backed Biden 62% to 26%.

The numbers were even more lopsided in Missouri, where 14% of voters were under 30 versus 31% over 65. Sanders won them with 70% of the vote. But that was no match for Biden’s 81% victory among retirement-age Democrats.

In state after state, the youngest voters have been staying home even as overall turnout skyrocketed. Youth voting was down 18% in New Hampshire, 9% in North Carolina and 20% in Texas. Obviously, this absence of young people has hindered Sanders’ campaign for the Democratic nomination, but it has also undermined his theory of electability and change, which depends on mobilizing huge numbers of people — and young people in particular — to execute a “political revolution.”

So what happened here? If young voters like Sanders so much (and they do; 52% have a “very favorable” or “somewhat favorable” view), why haven’t they turned out for him?

The first thing to say is that this relates to the larger question of perennially low youth turnout. In any given election year, the youngest adults always vote at lower rates than their older counterparts. That was true in 1972, the first national election after the 26th Amendment lowered the voting age to 18, and it was true for the 2018 midterms, when the youth share of the vote was 13% even as youth turnout more than doubled.

The traditional answer is apathy — that young voters just aren’t interested in politics or the political process, that they’re tuned out and disengaged. That’s why campaigns that want them focus so intently on energy and enthusiasm, why Sanders believed he could capture their concerns — speak to their hopes and needs — and in doing so bring them to the polls.

But what if apathy isn’t the problem? “It’s not that young people are disengaged; it’s not that they don’t care about the issues at hand; it’s just that they really struggle to follow through,” said John Holbein, an assistant professor of public policy and education at the University of Virginia and a co-author, with D. Sunshine Hillygus, of “Making Young Voters: Converting Civic Attitudes into Civic Action.”

Holbein and Hillygus find that young voters aren’t apathetic about politics and political life. Just the opposite. “By multiple metrics, most young people are politically interested and motivated,” they write. “And, despite the increased rancor in American politics, some measures find young people to be even more interested in politics in recent years than in the past.”

The issue isn’t interest, it’s structure. It is difficult to get anyone to do anything for the first time, and that is especially true for voting, which isn’t an easy process in the United States. Worse, many states are making it harder, with specific efforts to keep young people, and students in particular, away from the polls.

Last spring, for example, the Republican-controlled Texas Legislature outlawed any polling location that wasn’t open for the state’s 12-day early voting period, a move that forced a number of colleges and universities to close temporary voting sites on their campuses. Republicans in Florida, likewise, effectively banned early voting at state universities with a law requiring “sufficient non-permitted parking” at all early voting sites. That’s easy for rural and suburban locations, but it’s difficult for sites on densely constructed college campuses.

Even states that don’t target students and young people for voter suppression still require prospective voters to register if they want to cast a ballot. And that, Holbein said, is a real problem. “When you take away an arbitrary obstacle like voter registration, youth turnout goes up quite a bit.”

If you take a broader view of obstacles to the vote — if you look beyond administrative burdens like registration and voter identification — there’s the simple fact that being young is difficult. “Young people are coming into their own,” Holbein said. “They are leaving home, they are learning to be adults, and in that experience of managing their lives, voting is one of the things that falls by the wayside.”

Without experience and familiarity, young people lack the confidence to vote, to say nothing of other forms of political participation like canvassing or working the polls. They don’t think they know enough and don’t feel the kind of efficacy that drives older voters to the polls at high rates. The solution, Holbein and Hillygus argue, is comprehensive civics education that provides “knowledge and experience grounded in awareness of the factors that shape voter participation.” Young people, in other words, need to learn how to be citizens. And the extent to which we don’t teach those skills greatly depresses youth participation in politics.

Liberalizing voting laws and improving civics education are long-term projects. In the meantime, there are things a campaign like Sanders’ can do to improve youth turnout and bring those supporters to the polls. In addition to stoking interest, a campaign like Sanders’ can educate young voters about the process — not just by telling them to register, but also by walking them through the process itself and doing the work of a civics curriculum should have already done.

Voting is a habit; once people start, they tend not to stop. It may be too late for Sanders, but future youth-centered candidates might want to begin their campaigns with dedicated, practical outreach to people who want to participate but need a little help with the follow-through.

It’s possible that there is an upper limit to youth turnout, that at a certain point the youngest Americans just aren’t going to vote at the same rates as their parents and grandparents. But we haven’t come anywhere near it. For progressives in particular, there is a lot to gain in investing as much as possible into turning interested young people into dedicated participants. The effort put into making young voters today won’t pay off just in 2020; it could pay off the next time progressives are fighting for control of the Democratic Party.

Jamelle Bouie

Jamelle Bouie is an Op-Ed columnist for The New York Times.