Senator Bernie Sanders could always draw a crowd — more than 20,000 in New York City at his campaign’s peak — and it could seem from the outside that his followers were supportive of his every move during his presidential runs. The most fervent mobilized quickly against his opponents, deriding Hillary Clinton, criticizing Pete Buttigieg as inauthentic and casting Senator Elizabeth Warren as insufficiently progressive. The small donations amounted to fund-raising records.
But this week, when Mr. Sanders endorsed former Vice President Joseph R. Biden Jr. and called for his supporters to do the same, his announcement was met with healthy skepticism by some in his own base. Top surrogates like Representatives Alexandria Ocasio-Cortez of New York and Pramila Jayapal of Washington said they would not immediately echo his actions. Leaders of progressive grass-roots groups signaled they wanted to see more policy concessions from Mr. Biden.
Some members of the Sanders campaign staff clarified that their former boss was speaking for himself.
The space between candidate and movement, between figurehead and the political revolution he inspired, exposed a key element of the relationship between Mr. Sanders and his supporters.
They are loyal not to the man himself, but to the revolution he talked about. While opponents dismissed the crowds and donors as a cult of personality, the lock step of Mr. Sanders and his supporters is a marriage of ideas — many of which he has championed for decades.
And it’s going to take more than a live stream, even one with their beloved democratic socialist from Vermont, for Sanders supporters to fully get on board with the idea of Biden for President.
Ms. Jayapal, who backed Mr. Sanders and is a co-chair of the Congressional Progressive Caucus, said in a phone interview that “Mr. Biden will have to step up” if he wants enthusiastic support from the left wing of the party. She was one of several close allies of Mr. Sanders who were informed over the weekend that he intended to endorse Mr. Biden, according to people familiar with the discussions.
“This is a party that very much wants to be unified, but that will not be as easy as turning a switch and Bernie Sanders says vote for Joe Biden or Pramila Jayapal says vote for Joe Biden and everybody votes for Joe Biden,” Ms. Jayapal said. “There has to be real movement from Vice President Biden.”
Representative Ilhan Omar of Minnesota, who also endorsed Mr. Sanders, said: “The progressive movement has never been about one individual. It is about issues.”
“Our focus now should be on ensuring that we get the most bold, progressive agenda possible from our Democratic candidate — because that is what Americans want,” Ms. Omar said in a statement.
It was an undeniable political success for Mr. Biden to secure the swift endorsement of his chief primary rival, who dropped out the Democratic primary just last week. The hope among Mr. Biden’s allies is that the move by Mr. Sanders will be a catalyst for a united Democratic Party to defeat President Trump, a sign of party-wide political alignment against a common enemy.
At the very least, Mr. Biden has seemingly avoided problems faced by Mrs. Clinton in 2016, when she spent weeks being needled by Mr. Sanders even after it was clear she would be the nominee. Though Mr. Sanders did endorse Mrs. Clinton, and she embraced some of his more left-wing priorities as he campaigned for her on the trail, she never had the full-throated backing of the party’s progressive base, and fell flat on Election Day.
This time, Mr. Sanders backed Mr. Biden just five days after leaving the race himself. However, for Mr. Sanders’s endorsement to have maximum political impact, his most energized supporters — mainly young people, progressives and many Democrats in Western states with heavy Latino populations — have to come along, too.
Young people were a key part of President Barack Obama’s winning coalitions, but they did not support Mr. Biden in the primary. Polling has consistently shown that Mr. Biden’s voters skewed older and Mr. Sanders had more support not only among Gen Z voters at the far end of the spectrum, but also among millennials and voters up to 45.
The legions of activists who backed Mr. Sanders will also be important in state and local races, as Democrats seek an all-hands effort to win back the state and local seats that they lost during Mr. Obama’s presidency.
This is why progressive leaders still believe they have leverage to negotiate with Mr. Biden’s team for more policy concessions, even now that he is the presumptive nominee and has secured the endorsement of Mr. Sanders. They argue that Mr. Biden must recognize that even though they were defeated in the primary, the left’s energy is important for any general election coalition. They also believe the coronavirus pandemic has exposed cracks in the economy and public sectors that may lead voters to embrace left-wing solutions once seen as fringe.
“I don’t feel entitled to be paid attention to,” Ms. Ocasio-Cortez said in a recent interview with The New York Times. “But normal Washington politics has a disdain for advocates and activists and grass-roots community organizers. And, you know, we have an opportunity to change that and to really take these people seriously.”
In nominating a candidate without robust support from young people, Democrats are already “playing with precedent,” she added, “because nominees who have not had youth support do not fare well historically in November.”
In addition to the Sanders endorsement, Mr. Biden announced an initiative on Monday aimed at winning progressive support: joint policy task forces with the Sanders campaign covering issues like the economy, education, immigration, climate change and criminal justice.
In the last month, the Biden campaign has reached out to progressive leaders and policy experts to find areas of common ground, but some outreach has fallen flat, like the health care proposal to lower the Medicare age to 60 — which Ms. Ocasio-Cortez called “almost insulting.”
“Getting Bernie is not enough,” said Evan Weber, political director at Sunrise Movement, the youth-led climate activist organization that endorsed Mr. Sanders and was one of several groups to lay out their priorities for the former vice president in an open letter.
The open letter from the progressive groups mentioned policy task forces, and also asked Mr. Biden to include elected officials who backed Mr. Sanders or Ms. Warren on campaign policy and strategy.
“Mr. Biden must engage and reach out and show he’s the candidate for the full breadth of the Democratic coalition,” he said.
Max Berger, who was the director of progressive outreach for Ms. Warren’s campaign and previously worked with Mr. Sanders’s political group Our Revolution, said Mr. Biden’s task with young voters was pretty simple — support the policies that excite them.
“Young people are not buying what Joe Biden is selling,” he said. “And Bernie can help with the advertising, but Biden needs to change the product.”
Mr. Berger added that “Biden’s team should get on TikTok and look at all the videos of teens posting about crying” while thinking about having to knock on doors for Mr. Biden in November. These are young voters who want Mr. Trump out of the White House, and are not, at the moment, happy with their options, he said.
“Getting Bernie on board is incredibly useful,” Mr. Berger said. “Now get the people.”
Mr. Biden has acknowledged that he needs to do better with younger voters. In recent weeks, he embraced a version of the tuition-free college initiative once championed by Mr. Sanders, and recently announced his support of an expanded student debt forgiveness program.
In Monday’s live stream with Mr. Sanders, Mr. Biden implied that he was hoping that support from Mr. Sanders would help him with both young people and among progressives.
For most of the Democratic primary, he focused on a message of electability — that he was the person Democrats could trust to beat Mr. Trump. But, with Mr. Sanders in split screen, he cast himself as interested not just in winning, but also in progressive change.
“Your endorsement means a great deal,” he said, pledging to govern as a president who “goes down in history, with your help, Bernie, as one of the most progressive administrations since Roosevelt.”
Still, skepticism persists on the left. And the words of progressive leaders not named Bernie Sanders provided Mr. Biden with a much more ominous warning. Without real concessions of power, they said, the endorsement of Mr. Sanders will have small political coattails and endanger the party’s chances in November.
“We have the potential to move this country to unity and to move Democrats to unity,” Ms. Jayapal said. “But it will require not only progressives saying, ‘OK, we’re ready.’ It will require Joe Biden stepping in and saying, ‘I welcome you and here’s what I’m doing to inspire you.’”