A Warning on the Accuracy of Primary Polls
After another wild polling ride in Michigan, it is time for a reflection on just how accurate primary and caucus polls have been — both in an absolute sense and as compared with past years. This discussion, of course, also has implications for the FiveThirtyEight forecast model, which is based upon the polls.
The short version: the polls have been reasonably good in the last few days before the election. Not perfect by any means — worse than general election polling typically is, for example. But no worse, and probably somewhat better, than in past primaries. . .
On the other hand, the polls have been pretty awful at most points prior to about three days before the election, seeing surges and momentum shifts that often dissipated.
http://fivethirtyeight.blogs.nytimes.com/
