Few news organizations gave the story more velocity than The New York Times. On the morning of Oct. 29, Comey stories stretched across the print edition’s front page, accompanied by a photo showing Clinton and her aide Huma Abedin, Weiner’s estranged wife. Although some of these articles contained detailed reporting, the headlines focused on speculation about the implications for the horse race — “NEW EMAILS JOLT CLINTON CAMPAIGN IN RACE’S LAST DAYS.” […]

Clinton’s standing in the polls fell sharply. She’d led Trump by 5.9 percentage points in FiveThirtyEight’s popular vote projection at 12:01 a.m. on Oct. 28. A week later — after polls had time to fully reflect the letter — her lead had declined to 2.9 percentage points. That is to say, there was a shift of about 3 percentage points against Clinton. And it was an especially pernicious shift for Clinton because (at least according to the FiveThirtyEight model) Clinton was underperforming in swing states as compared to the country overall. In the average swing state, Clinton’s lead declined from 4.5 percentage points at the start of Oct. 28 to just 1.7 percentage points on Nov. 4. If the polls were off even slightly, Trump could be headed to the White House. […]

So while one can debate the magnitude of the effect, there’s a reasonably clear consensus of the evidence that the Comey letter mattered — probably by enough to swing the election. This ought not be one of the more controversial facts about the 2016 campaign; the data is pretty straightforward. Why the media covered the story as it did and how to weigh the Comey letter against the other causes for Clinton’s defeat are the more complicated parts of the story.

Nate Silver, The Comey Letter Probably Cost Clinton The Election, FiveThirtyEight, 3 May 2017

Added to diary 30 January 2018