The 2016 US presidential election continues to surprise and confuse. The latest twist has revealed that, after months of dismissing rumours about her health as conspiracy theories, we learn that Hillary Clinton has pneumonia. She had to leave a September 11 memorial event on Sunday, not entirely under her own steam, and has cancelled a two-day campaign swing through California.

There can be no doubt that this is bad news for Mrs Clinton’s campaign. It is not just that she has taken ill and will miss an unknown number of days of campaigning. It is also that her health problems and her campaign’s apparent efforts to hide them fall into two pre-existing narratives. Mr Trump and his surrogates have for months been seeding the media ground with the twin notions that Mrs Clinton is both frail and deceptive.

Developments that bolster longstanding narratives tend to be particularly bad for a candidate’s standing. Mitt Romney’s gaffe, during the 2012