5. Polling and big data don’t automatically generate the right moves. Campaign strategists have used polls to shape messages since the 1960s, often shrewdly. But poll interpretation is not a science but an art. The Clinton campaign didn’t notice its candidate’s weakness in the Outstate (outside million-plus metro areas) Midwest, because those areas are just one subgroup in statewide polls (though Iowa polls were a clue). That weakness swung 70 Obama electoral votes to Trump.

Big data interpretation must be combined with what German military thinkers called Fingerspuzengefuhl, fingertip feeling. The Clinton campaign had scads of big data in its Brooklyn headquarters, but was so rigid in its application that it ran more late-campaign TV ads in Omaha (for the Nebraska 2nd District’s 1 electoral vote) than in Wisconsin and Michigan (26 electoral votes).