Presidential candidates Sen. Kamala Harris and Julian Castro were among prominent Democrats calling on Virginia Gov. Ralph Northam to resign Friday night over a photograph of him in a racist costume. Ms. Harris, California Democrat, tweeted, “Leaders are called to a higher standard, and the stain of racism should have no place in the halls of government. The Governor of Virginia should step aside so the public can heal and move forward together.” Mr. Castro, mayor of San Antonio, Texas, said it “doesn’t matter if he is a Republican or a Democrat.”