Our cover this week comes from the Democratic convention in Chicago. It has been a joyous, heady celebration by a political party that only a month ago thought it was staring at defeat. I have listened to one speaker after another tease Donald Trump for being mean-minded, complaining, selfish, negative and annoying—like your neighbour’s incessant leaf-blower, said Barack Obama; and they have contrasted him with their own nominee, Kamala Harris. The convention was all about her character and her life-story. Americans now know not only that she’s brave and kind and dedicated to public service, but also that she worked at McDonald’s and that every year she teases her husband by playing the rambling voicemail he left asking her for a first date.

So far, it’s working. Since Joe Biden stepped back, near-certain defeat has turned into a race that is too close to call. But we argue that Ms Harris needs more. To strengthen her claim to the White House she should also unspool a single thread running from her life-story to her principles and to show how that leads to a programme for government. She has reasons for building her campaign around personality. Her overriding task is to defeat Mr Trump, and it is a vital one in which guile and cunning are permitted. But you can be desperate for Ms Harris to win against Mr Trump and still wonder how good she would be in office.