538: Exit polls are re-calibrated as the night to match actual votes.

It’s true: the exit poll results are re-calibrated as the night goes along to match the actual vote count. In fairness, however, the people who conduct exit polls — and the networks and newspapers who pay for them — are quite insistent that exit polls are not intended to project election results and instead are mostly meant for demographic analysis after the fact. And for the record, while the exit polls were off on the Democratic side tonight, they’ve had a pretty good campaign cycle overall — they were quite good on the GOP side tonight, for instance, providing an early indication that Trump would probably win.



http://fivethirtyeight.com/live-blog/new-york-primary-presidential-election-2016/