NATE SILVER: You Know, There Really Was A Liberal Media Bubble.

It’s hard to reread this coverage without recalling Sean Trende’s essay on “unthinkability bias,” which he wrote in the wake of the Brexit vote. Just as was the case in the U.S. presidential election, voting on the referendum had split strongly along class, education and regional lines, with voters outside of London and without advanced degrees being much more likely to vote to leave the EU. The reporters covering the Brexit campaign, on the other hand, were disproportionately well-educated and principally based in London. They tended to read ambiguous signs — anything from polls to the musings of taxi drivers — as portending a Remain win, and many of them never really processed the idea that Britain could vote to leave the EU until it actually happened.

So did journalists in Washington and London make the apocryphal Pauline Kael mistake, refusing to believe that Trump or Brexit could win because nobody they knew was voting for them? That’s not quite what Trende was arguing. Instead, it’s that political experts aren’t a very diverse group and tend to place a lot of faith in the opinions of other experts and other members of the political establishment. Once a consensus view is established, it tends to reinforce itself until and unless there’s very compelling evidence for the contrary position. Social media, especially Twitter, can amplify the groupthink further. It can be an echo chamber.

Can be, and is.