WASHINGTON — Joe Biden consolidated his gains as he races to the Democratic nomination, dominating a trio of primaries last Tuesday among voters male and female, rich and poor, white and nonwhite, college and high school graduates.

But there was one glaring exception: young voters.

Voters under 45 continued to support Bernie Sanders by huge margins in Florida, Illinois and Arizona even as other groups came around to Biden. The gap has been largest with voters in their 20s or teens, mirroring a problem that hurt Hillary Clinton in key states in 2016: a lack of excitement among the young.

“I'm deeply concerned about the impact that a lack of enthusiasm from young voters could have in a general election,” said Neil Sroka, a spokesman for Democracy for America, a progressive advocacy group that backs Sanders. “The consistent concern has been that nominating Vice President Biden would be essentially a repeat of the 2016 election.”

Failing to excite young voters in the primary has been a “significant red flag” for Democrats in recent decades, Sroka said: Barack Obama and Bill Clinton, who were backed by young people, went on to win the election, while Hillary Clinton, John Kerry and Al Gore lacked that enthusiasm and ended up losing.

Biden’s dilemma reflects a generational party divide between older moderates who were content with the Obama-era status quo, and younger voters hungry for the disruptive change Sanders represents as they risk becoming the first generation in U.S. history to be economically worse off than their parents.

Biden is winning the proxy war because older voters have turned out in larger numbers than younger ones. But to complete the job and win the presidency, Biden recognizes he has work to do — he can’t afford for young people to stay home or vote third party, as many did in the last election.

'Take this very seriously'

Voters under 30 made up 19 percent of the electorate in 2016 and in 2012, but Hillary Clinton’s margin of victory with this group was five points lower than Obama’s, according to exit polls.

The numbers were devastating in swing states that decided the election. In 2012, Wisconsin voters under 30 backed Obama by 23 points; in 2016, that group dipped as a share of the electorate and Clinton won them by a mere 3 points. In 2012, Pennsylvania voters under 30 supported Obama by 28 points; in 2016 they favored Clinton by 9 points.

An Economist/YouGov trial heat survey this month between Biden and President Donald Trump found Biden leading by 4 points overall, and winning the same 55 percent of voters under 30 that Clinton won in 2016. Eight percent were unsure who they’d vote for, and another 8 percent said they would not vote, the poll said. Biden performed better than Clinton did with elderly voters.

“I think Biden needs to take this very seriously, both in terms of understanding that it’s a real possible problem for him but also a real opportunity," said Democratic pollster Andrew Baumann, who has studied the voting behavior of young people. "He's got some of the same challenges (that Clinton had) to make them understand that he’s not an enemy of what Bernie is trying to accomplish. He clearly isn’t, but he has some work to do convincing them of this.”

Baumann said young voters can be moved if he conveys the need for fundamental change, with policies to back it up like anti-corruption measures, getting money out of politics and standing up to oil companies and Wall Street banks. He said that climate change is the No. 1 issue for many young people and that Biden could make it a larger focus of his campaign, perhaps even meet with Sunrise Movement activists to hear their concerns.

The Biden campaign sees three major differences with Clinton’s 2016 campaign, according to a source familiar with its thinking. The first is that Trump is president, unlike four years ago when many young people were complacent because they assumed he’d lose. The second is that Biden’s 2020 platform is more progressive than Clinton’s was in 2016. And the third is that Biden and Sanders like each other personally, which will make it easier to coalesce.

Biden has sought to address the problem by rolling out two new policy planks last weekend that would benefit young people: tuition-free public colleges and universities, and allowing Americans to clear out student debt in bankruptcy. At the debate last Sunday, he promised to pick a woman as running mate.

“Let me say, especially to the young voters who have been inspired by Senator Sanders: I hear you,” he said Tuesday in his victory speech. “I know what is at stake.”

Democratic pollster Margie Omero said Biden’s strong support for gun control and his relatively early embrace of same-sex marriage could be valuable pitches to young people. She said his experience dealing with crises is also an asset as the coronavirus outbreak sends students home from college and forces them to self-contain amid the pandemic.

“Younger voters, generally speaking, are less engaged. They are going to need to get reacquainted with Joe Biden,” she said, adding that he’ll need surrogates to help him.

'Are you insane?'

Others say the problem cannot be fixed with cosmetic tweaks.

Max Berger, a former aide on Elizabeth Warren’s presidential campaign, said Biden suffers from a trust deficit with young voters who worry he doesn’t understand their problems and is resistant to ideas that match their scale, whether it’s the Green New Deal or eliminating student debt.

“My hope is they're smart enough to realize it's not a marketing problem, it's a product problem. They're selling the wrong product,” he said. “When he says ‘I think Republicans will go back to normal,’ young people are like: Are you insane?”

Berger said Democrats look like two parties — an older moderate one represented by Clinton and Biden, and a younger progressive party that wants leaders like Sanders and Rep. Alexandria Ocasio-Cortez, D-N.Y. He said that if Biden wants to excite the younger wing, he needs to make policy concessions to the ideas that motivate them and treat them like a coalition partner in a parliamentary system.

“If you're under 35, you grew up under a botched war of choice, a recession, the Trump administration and now a pandemic and potentially another recession,” Berger said. “The expectation of the status quo does not make any sense if you're under 35. For people whose whole political outlook is just put Humpty Dumpty back together again — that doesn't work.”

“In some sense, our generation wants normalcy,” he said. “We've just never experienced it.”

After a string of defeats in the March 10 primaries, Sanders, who has vowed to support Biden if he's the nominee, suggested the former vice president can only win young voters though the power of his ideas.

“Today I say to the Democratic establishment: In order to win in the future, you need to win the voters who represent the future of our country. And you must speak to the issues of concern to them,” he said.

Sroka said the nostalgic undertones in Biden's message won't resonate with millennials or the Gen Zers or those voters in between.

“His campaign is essentially 'Make America 2015 Again,'” Sroka said. “For older resistance crusaders, the moment the world went off a cliff was the 2016 election. For folks under the age of 35, the world was going off a cliff long before Trump got there.”