“MINI MIKE is a 5’4” mass of dead energy,” President Donald Trump tweeted on February 13th. Two days earlier he had sneered at his rival’s golf swing: “Mini Mike is a short ball (very) hitter. Tiny club head speed.” Mr Trump was, of course, referring to Michael Bloomberg, the former mayor of New York City, who is vying with several other Democratic Party hopefuls to run for president in November. The billionaire businessman (who is in fact five-foot-seven) is the latest in an eclectic and ever-lengthening list of supposedly diminutive figures whom Mr Trump (who stands at six-three) has ridiculed—among them Kim Jong Un, the dictator of North Korea (around five-seven), and Sadiq Khan, the mayor of London (five-five). These jibes are often dismissed as frenzied fits of Twitter-induced rage. Yet there may be a method to Mr Trump’s madness.

Presidents are becoming taller relative to average Americans (as measured by army records of recruits of the same age cohort); the last president shorter than this mean was William McKinley, elected in 1896. And being short can hinder a candidate’s presidential prospects. A paper published in 2013, by psychologists at the University of Groningen in the Netherlands, analysed the results of American presidential elections dating back to 1789. They found that taller candidates received more votes than shorter ones roughly two-thirds of the time. And the taller the candidates relative to their opponents, the greater the average margin of victory. Among presidents who have sought a second term, winners have been two inches taller, on average, than losers. The authors conclude that height may explain as much as 15% of the variation in election outcomes.