Barack Obama used to be confident America would survive Donald Trump. He’s not so sure anymore. The 44th president can still draw a crowd of thousands or dial Gavin Newsom’s cell phone to strategize about the California governor’s redistricting push. But friends who talk to him say it’s become clear that eight years out of the White House, darkness and anxiety have crept in on Obama’s message of hope and change. After deliberately stepping back during the Biden years — while remaining the party’s biggest fundraiser even then — Obama and his aides are reworking his longstanding strategy of minimizing...