JOSEPH CAMPBELL: Read this before you buy the ‘blue tsunami’ hype.

The news is awash these days with poll-inspired expectations about Democrats winning big in next month’s midterm elections. USA Today declared the other day that “the expected blue wave could be even bigger than expected, and could not only give Democrats control of the House, but also the Senate.” Even more expansively, Huffington Post proclaimed: “Historic victories are seemingly within grasp” for Democrats.

And yet, solid reasons exist for treating such poll-based narratives cautiously, even warily, given that surveys are inherently fragile instruments for measuring an ephemeral electorate. As data journalist Nate Silver has noted, “It’s not unreasonable to approach election polls from a position of mild — maybe even more-than-mild — skepticism.”

This is not to say poll-driven expectations are bound for error. They might be accurate; the Democrats might enjoy a “blue tsunami” of electoral success next month.

But there are compelling reasons for tempering pre-election headiness — reasons that are rooted in polling’s checkered past. The following summary of recent shortcomings in election polling offers context and justification for tapping the brakes about poll-driven high hopes this year.

Read the whole thing – and don’t get cocky, to coin an Insta-phrase.

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