In a lengthy video announcing his support, one day after Mr. Sanders himself endorsed Mr. Biden, Mr. Obama praised Mr. Sanders for setting a new agenda for the party and signaled that more progressive ideas would be reflected in Mr. Biden’s campaign going forward. At the same time, he urged fortitude in the face of the coronavirus, sounding less like a campaign-trail endorser at points than a president addressing a nation in crisis.
His goal could not have been clearer: to energize the many younger and more progressive voters who dislike or distrust Mr. Biden, and bridge the party’s ideological divisions in a way that he may be uniquely positioned to do.
Appealing directly to Mr. Sanders’s supporters, he underscored the pivot Mr. Biden has been trying to make since wrapping up the nomination: from an argument, essentially, for restoring the pre-Trump status quo to an argument that this is insufficient. It is the argument Mr. Sanders and other progressive candidates — like Senator Elizabeth Warren of Massachusetts, whose call for “big structural change” Mr. Obama overtly echoed — made all along.