Young supporters of Sen. Bernie Sanders (I-Vt.) attend a campaign rally in Grand Rapids, Mich., on March 8. New polling shows the youngest Sanders supporters are relatively bearish on former Vice President Joe Biden, prompting some concerns about turnout in November. (Scott Olson/Getty Images)

2 in 3 Bernie Sanders supporters are under the age of 45, more than twice the share of Biden’s supporters.

47% of the youngest Sanders backers have an unfavorable view of Biden vs. 44% who have a favorable view.

Youngest Sanders supporters are slightly more inclined to opt out of a Biden-Trump choice in November than older backers.

Hours after Sen. Bernie Sanders (I-Vt.) dropped his bid for the Demoratic presidential nomination, a group of eight organizations representing young liberals came out with a warning for Joe Biden, who had just become the party’s presumptive nominee. In an open letter Wednesday, the groups said Biden’s message of a “return to normalcy” isn’t enough for younger voters, and called on him to embrace the kind of revolutionary change sought by Sanders and his supporters and viewed with some skepticism by the broader Democratic electorate. The letter highlights a challenge for Biden as his campaign works to unify the party and avoid the drop in support from young voters that hindered Hillary Clinton’s 2016 campaign against Donald Trump after a bruising primary against Sanders. “There is a trust gap between Biden and voters under 45, just like there was with Hillary Clinton,” said Waleed Shahid, a spokesman for Justice Democrats, one of the letter’s signatories, in an interview prior to Sanders’ exit from the race. The Biden campaign did not respond to a request for comment.

New Morning Consult data shows two-thirds of Sanders supporters in the Democratic primary are under the age of 45, more than twice the share of Biden’s supporters who are the same age. But that demographic seems to have contributed to Sanders’ downfall this year: Exit polling conducted on Super Tuesday showed younger Americans did not vote for Sanders at the rate they did in 2016. However, their presence at the polls in the fall is “necessary to defeat Trump and will only become more essential to the Democratic Party’s future,” Shahid said. Sanders supporters are more likely to hold a dimmer view of Biden than the average Democrat — especially those ages 18-34, 47 percent of whom view Biden unfavorably. The responses were collected March 18 through April 7 among roughly 15,000 Democratic primary voters who said they would vote for Sanders even as it became increasingly clear that Biden was en route to clinching the nomination. The polling has a margin of error of 1 percentage point.

While Sanders supporters have mixed views about Biden, they’re more certain about their antipathy toward the president, regardless of age. Overall, about 85 percent of both Sanders’ supporters and Democrats disapprove of Trump’s job performance, and more than 7 in 10 do so strongly, 30 points more than the share who have somewhat or very unfavorable views of Biden. Nathan Gonzales, a nonpartisan political analyst and publisher of Inside Elections, said the best person to shore up Biden’s backing among Sanders supporters is Trump himself. “They spent months trying to defeat Biden, so it’s not a surprise they’re slow to liking the guy,” he said. “It might take time for Sanders supporters to say they’ll support Biden, but it will happen. The vast majority of them will prefer Biden over four more years of President Trump.” In a head-to-head matchup, only 7 percent of Sanders supporters said they would vote for Trump in November, according to the latest tracking, down from the 12 percent estimated to have done so in 2016. There was little difference by age; if anything, younger Sanders voters were slightly less likely to say they would vote for Trump in November or hold favorable views of the president than older voters who backed Sanders. But younger Sanders supporters were also more inclined to opt out of the two-person choice, with 15 percent of those ages 18-34 saying they did not know whom they would vote for in November.