This is an abbreviated version of a commentary originally posted at The Hill; the commentary was drawn from Lost in a Gallup: Polling Failure in U.S. Presidential Elections.

It’s axiomatic that pre-election polls set the narrative for U.S. presidential campaigns. … polls are central to shaping conventional wisdom about the competitiveness of the races. But when polls misfire, journalism can falter, too, leaving the news-consuming public feeling misled, ill-served, and even a bit contemptuous.

That polling failure can give rise to journalistic error has been evident for more than 70 years, at least since the “Dewey defeats Truman” election of 1948. That was when poll-based predictions gave President Harry Truman no chance of reelection, when Republican Thomas E. Dewey supposedly needed only to count the days to his presidential inauguration. …