Conversation survey data shows what…pretty much all of the relevant data shows about the effect of James Comey deciding to kneecap Hillary Clinton based on absolutely nothing less than two weeks before the election:
Most decisively, there was a sudden change in the net sentiment results that followed immediately after FBI Director James Comey released his Oct. 28 letter to Congress about a renewed investigation of Clinton emails. Immediately afterwards, there was a 17-point drop in net sentiment for Clinton, and an 11-point rise for Trump, enough for the two candidates to switch places in the rankings, with Clinton in more negative territory than Trump. At a time when opinion polling showed perhaps a 2-point decline in the margin for Clinton, this conversation data suggests a 28-point change in the word of mouth “standings.” The change in word of mouth favorability metric was stunning, and much greater than the traditional opinion polling revealed.
Based on this finding, it is our conclusion that the Comey letter, 11 days before the election, was the precipitating event behind Clinton’s loss, despite the letter being effectively retracted less than a week later. In such a close election, there may have been dozens of factors whose absence would have reversed the outcome, such as the influence campaign of the Russian government as detailed by US intelligence services. But the sudden change in the political conversation after the Comey letter suggest it was the single, most indispensable factor in the surprise election result.
This conclusion helps us to understand how it is possible that the polls were generally correct about a Clinton lead through most of the campaign, but nevertheless Trump still won because of a late October surprise. In other words, pollsters and the media were likely correct that Clinton was “winning” during most of the campaign.
Obviously, in roughly 99% of cases people demanding “MOAR EVIDENCE” about the Comey effect are making the demand in bad faith, because no alternative hypothesis to “Hillary Clinton lost because, in her perfidious neoliberalism, she failed to understand that marginal voters in every jurisdiction in the country have exactly the same policy preferences and priorities as Brooklyn socialists” is ever going to be entertained. (Sometimes, this will be followed by demands that nobody else discuss any other variable either.) But the evidence that Comey’s intervention was decisive ceteris paribus is about as clear as any such counterfactual could be.