With Joe Biden the last man standing in the Democratic primary race for president, there is increasingly anxious discussion within the party about how — or even if — the former vice president can win over disappointed progressives. Of particular concern are the younger voters whose energy and idealism fueled the campaign of Bernie Sanders.

On April 8, just hours after Mr. Sanders suspended his campaign, a collection of eight progressive groups “building political power for young people” sent Mr. Biden a four-page letter detailing how he could win their support. Their to-do list called on him to embrace a range of progressive policies — including Medicare For All, the “frameworks of the Green New Deal” and a wealth tax — as well as to add progressive advisers to his campaign and, later, his administration. “With young people poised to play a critical role deciding the next president, you need to have more young people enthusiastically supporting and campaigning with you to defeat Trump,” they wrote.

The next day, the former candidate Tom Steyer added his voice to the call, urging Mr. Biden to pursue young progressives. “There’s going to have to be a process to convert” them, Mr. Steyer told Politico.

This is a daunting challenge. Mr. Biden is a 77-year-old moderate who has spent his entire adult life in politics and in many ways embodies The Establishment. So far, he has been running on a backward-looking platform of restoration — not exactly a message to electrify the youth vote. Yet regardless of how hard Mr. Biden might try to overhaul his image, the unfortunate electoral reality — dramatically spotlighted by the Sanders campaign — is that betting on the youth vote remains a losing proposition. An enduring truth of politics is that, whether in presidential years or midterm races, younger voters consistently turn out at a lower rate than older ones. (The 18-29 year olds trail the 30-44-year-olds, who trail the 45-59- year-olds. Voters 60 and up are the Election Day rock stars.) Until that changes, young people will have a tough time getting their concerns taken as seriously as they deserve.