Though the president is fiercely loyal to his children, some observers wonder if deepening and dangerous controversy might test such bonds to breaking point
It was an unseasonably cool day in New York. At 1.50pm on 9 June, Hillary Clinton tweeted that Barack Obama was backing her for US president. Half an hour later, Donald Trump tweeted: “Obama just endorsed Crooked Hillary.” At 2.27pm, Clinton replied: “Delete your account”. It was the most retweeted post of her campaign.