Harry Truman, 33rd American president, often and proudly displayed the Chicago Tribune headline the day after the 1948 election: ‘Dewey Wins’, referring to the near-universal prediction that the New York governor would win the White House.

Polling has come a long way since then. But it didn’t even need polls in 1948. New York Times articles repeatedly noted the growing crowds for the president and had to rationalise the slim pickings Dewey was getting.