The Left Is Still Leery of Biden. Here’s How He’s Reaching Out to Them.

Through conversations on Capitol Hill, engagement with local activists and policy nods toward Elizabeth Warren and Bernie Sanders, Joseph R. Biden Jr.’s campaign and its allies are ramping up overtures to progressives, aiming to improve Mr. Biden’s standing with a key part of the Democratic coalition in an effort to unite the party around his potential nomination.

Mr. Biden has assembled a broad base of support from black and suburban white voters as he has racked up a string of victories over the last month. But many younger and left-wing...