It's been happening for years now. On the day after elections like last Tuesday's, media figures begin navel gazing to figure out how pre-election polls, created by dozens of independent pollsters using dozens of different methodologies, could all find the same thing but turn out to be so wrong once the election results are in.
The presumption is that the results are always right, and if they don't match the pre-election polling, its the polling that must be wrong, as opposed to the election results.
On Wednesday morning, after Tuesday's mid-term election surprise in which Republicans reportedly won handily in race after race despite pre-election polls almost unanimously predicting much closer races or outright Democratic victories, FiveThirtyEight statistics guru Nate Silver declared "The Polls Were Skewed Toward Democrats".
His analysis of aggregated averages from dozens of different pollsters and polls this year found that the performance of Democrats was overestimated by approximately 4 percentage points in Senate races and 3.4 points in gubernatorial contests. Silver's assessment relies on a "simple average of all polls released in the final three weeks of the campaign," as compared to the (unofficial and almost entirely unverified) election results reported on Tuesday night. He doesn't suggest there was anything nefarious in the polling bias towards Dems this year, simply that the pollsters got it wrong for a number of speculative reasons.
Citing the fact that nearly all of the polls suggested Democrats would do much better than they ultimately did, when compared to the reported election results, Silver asserts it wasn't that the polls were more wrong that usual, per se, but that almost all of them were wrong in a way that appears to have overestimated Democratic performance on Election Day.
"This year's polls were not especially inaccurate," he explains. "Between gubernatorial and Senate races, the average poll missed the final result by an average of about 5 percentage points --- well in line with the recent average. The problem is that almost all of the misses were in the same direction."
Silver is much smarter than I when it comes to numbers; I'm happy to presume he has the basic math right. But he seems to have a blind spot in his presumption that the pre-election polls were wrong and the election results were right. That, despite the lack of verification of virtually any of the results from Tuesday night, despite myriad and widespread if almost completely ignored problems and failures at polls across the country that day, and despite systematic voter suppression and dirty tricks that almost certainly resulted in election results (verified or otherwise) that were skewed toward Republicans...