By most measures, it is this overwhelming desire to defeat Mr. Trump that helps explain why the Democratic Party does not expect Sanders loyalists to be as disruptive to the electoral prospects of the party’s nominee as they were in 2016. Mr. Sanders is now keenly aware of the electoral power his loyal backers wield, and that their support for Mr. Biden could be a key factor in beating Mr. Trump. Never again, aides say, does he want to inspire the kind of divisiveness that some in the party still blame for the election of Mr. Trump. (Some detractors also see sexism in this more conciliatory approach, suggesting that his supporters harbored particularly visceral disdain for Mrs. Clinton because she was a woman.)
And while Mr. Sanders’s backers still bemoan the quick coalescence of his more moderate rivals behind Mr. Biden after the South Carolina primary, it is harder to assert that the process was rigged. After all, it seemed briefly as if Mr. Sanders would win.
After a strong showing in Iowa and a victory in New Hampshire, Mr. Sanders, then considered a front-runner, ran away with the Nevada caucuses. “We have just put together a multigenerational, multiracial coalition, which is not only going to win in Nevada, it’s going to sweep the country,” he told an exultant crowd in San Antonio that February night. He predicted a victory in Texas the next month.
That victory did not come, one of a string of losses on Super Tuesday that ground his momentum to a halt. Sidelined by the pandemic soon after, he surrendered the race to Mr. Biden. “I cannot in good conscience continue to mount a campaign that cannot win,” he said at the time, “and which would interfere with the important work required of all of us in this difficult hour.”
Sanders supporters say the swiftness with which his supporters have united behind Mr. Biden is a testament to how Mr. Sanders has approached this entire second presidential bid. They point in particular to his decision to exit the race in early April, before the race could become acrimonious, then almost immediately back Mr. Biden.
It was a striking departure from 2016, when he remained in the race even after it became increasingly clear he would not win. He did not endorse Mrs. Clinton until days before the convention, a decision that she and her aides maintain came too late and was too dutiful and halfhearted to unify the party behind her. (Mr. Sanders and his associates, by contrast, frequently note that he and Mr. Biden are friends.)
“I do think he’s certainly playing the political role that you would ask him to play,” said Faiz Shakir, who served as Mr. Sanders’s campaign manager for his second presidential bid.