The White House had expected Democratic unrest over Gaza to fade as President Biden picked up his campaigning against presumptive Republican nominee Donald Trump. Nine months before the election‚ the problem is worsening as Mr. Biden’s opposition to calling for a permanent cease-fire continues to stir anger in a coalition of voters that propelled his 2020 victory‚ from Black Americans to Muslim activists in must-win Michigan to young voters. Democrats have been broadly divided over Mr....