Ryan Cooper in The Week:
A recent review of studies convincingly argues that FBI Director James Comey's letter vaguely announcing a new chapter in the email investigation eroded Clinton's margins by enough to make her lose. It was a damning announcement, coming from a relatively respected institution, at about the worst possible time. There were also an unusually large number of undecided voters that late in the campaign, and the FBI's announcement got saturation coverage.
It's important to emphasize that in such a close election, there are dozens of things that could also have tipped the balance. The fact that it was close enough to tip in the first place shows that Clinton was a terribly weak candidate — it is a virtual certainty that had Obama been on the ballot, he would have weathered such a blow. But it's still highly alarming that without a single action taken by the head of the FBI, Donald Trump would not have been elected president.
And that's only the tip of the iceberg. As Glenn Greenwald demonstrates, much of the 2016 election played out as a proxy war between the pro-Clinton CIA and the pro-Trump FBI, with dueling op-eds, anonymous leaks, and accusations.
This kind of thing is perhaps the major reason to preserve due process and civil liberties in the security apparatus. One of the more shameful aspects of the Obama presidency was watching liberals reverse-engineer reasons for why Bush-era security policies were now good, as they became Obama-era security policies. The most common rationale they landed on was the usual one about there being a tradeoff between security and privacy, and in a dangerous world we've simply got to give the spooks greater latitude (read: break whatever laws they want).
This argument is trash for many reasons, but among them is that it presents an incomplete picture of what is being sacrificed. Individual privacy is harmed by dragnet surveillance and unaccountable security agencies, but so is the basic democratic nature of the political system.