WASHINGTON — Seven progressive groups made up of young activists wrote a letter to Joe Biden, the apparent Democratic presidential nominee, with a set of aggressive demands spanning policy and personnel to earn their support in the general election against President Donald Trump.

The letter, which comes hours after Sen. Bernie Sanders, I-Vt., ended his campaign, tells Biden that his pitch to "return to normalcy" won't earn the trust of younger generations or inspire them to vote, arguing that they were already falling behind economically before Trump took office.

"Exclusively anti-Trump messaging won't be enough to lead any candidate to victory. We need you to champion the bold ideas that have galvanized our generation and given us hope in the political process," read the letter, signed by the Alliance for Youth Action, Justice Democrats, the March for Our Lives Action Fund, NextGen America, Student Action, the Sunrise Movement and United We Dream Action.

The organizations, some of which endorsed Sanders in the primary, said they would spend more than $100 million to mobilize millennial and Gen Z Americans this cycle and asked Biden's campaign to ensure that their efforts are "backed-up by a campaign that speaks to our generation."

The groups call on Biden to endorse policy initiatives like "Medicare for All," canceling all student debt, taxing wealth and the Green New Deal framework of a fully clean energy economy by 2030. They make process demands like eliminating the legislative filibuster and adding seats to the Supreme Court. And they include personnel wishes like rejecting Wall Street or other corporate executives for important roles and picking a Homeland Security chief committed to "dismantling ICE and CBP as we know them," referring to Immigration and Customs Enforcement and Customs and Border Protection.

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The former vice president opposes some of those ideas outright, like single-payer health insurance, and his agenda doesn't go quite as far on others. Other issues they advocated for, like overhauling the immigration system and imposing new gun control measures, are part of Biden's agenda, which is already one of the most progressive of any modern Democratic nominee.

They also call on Biden to create a task force on young Americans, who were a key part of President Barack Obama's victories in 2008 and 2012 and may hold the keys to a possible Biden victory.

The progressive youth letter reflects a major challenge facing Biden ahead of the general election. Young voters aren't enthusiastic about him, but he needs their support to defeat Trump in the general election and avoid the fate of Hillary Clinton, who saw drop-offs from 2012 among voters under 30 in key states like Wisconsin and Pennsylvania, which decided the outcome.

Biden has work to do: A Quinnipiac poll Wednesday found his overall favorable-to-unfavorable rating tied at 43 percent, but among voters under 35, his unfavorables exceeded his favorables by 19 points. Trump still fared worse with those voters, underwater by 23 points.

Biden's campaign recognizes the challenge and reached out to those voters Wednesday. He alluded Wednesday to Sanders and "the millions of his supporters — especially younger voters — who have been inspired and energized and brought into politics by the progressive agenda he has championed."

"Bernie has done something rare in politics. He hasn't just run a political campaign; he's created a movement. And make no mistake about it, I believe it's a movement that is as powerful today as it was yesterday. That's a good thing for our nation and our future," Biden said in a statement.

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Young people are uniquely challenging to turn out and, more so than older Baby Boomers, often need to feel personally inspired by a candidate to vote. They backed Sanders by wide margins but didn't vote in big enough numbers to help him win. Still, Democrats lack a winning coalition without them.

Sanders told supporters in a video message Wednesday that Biden is "a very decent man, who I will work with to move our progressive ideas forward."

Biden included Sanders' slogan in his appeal to his voters.

"I'll be reaching out to you," he said in his statement. "You will be heard by me. As you say: Not me, us."