If Clinton significantly outperforms exit polls showing a close race tonight and wins by a fairly comfortable margin instead, will it be part of a broader pattern? Not really. We’ve been keeping track of how Clinton’s and Sanders’s actual results have compared to initial exit polls, and the differences have been pretty random over the course of the campaign.
With that said, sometimes a candidate whose supporters are more enthusiastic can be overrated by exit polls because of response bias — this was sometimes an issue for Obama during the 2008 campaign, and it’s plausible we could see something parallel happening with Sanders. Furthermore, pre-election polls showed a wider lead for Clinton than the exit polls did, and it’s usually worth taking a blend of exit polls and pre-election polls even when you have exit polls in hand.
