How the Polls Performed Part 2 - Democrats

So, now that the Democratic Primaries have wrapped up it is time to look at how the polls performed on this side. The same questions have been brought up in both the Republican and Democratic primaries about whether the polls were a good predictor or not.

I used the same method for the Democratic Primaries as the Republican Primaries:

The way in which I assigned how the averages of the polls did in each state was in three categories; over polled(with the addition of slight/very over polled), even, and under polled (with the addition of slight/very under polled).

If the polling averages were 2% or better I marked them as even.

If the polling averages were between 3-4% I marked them as slightly over/under.

If the polling averages were between 5% I marked them as over/under.

If the polling averages were over 7% I marked them as very over/under.

The polls on the Democratic side were about the same as the Republican. In states that had enough polls to have an average those polls were a fair predictor of how the results would look. In those states where there were not enough polls and the last poll was used they were not a reliable predictor.

Essentially the more polls in the state the better the polls did and the less polls the worst.

I looked at 38 states. 19 states and territories either didn't have enough polling or any polling for testing. None of the territories or Democrats Abroad were tested. Clinton won all of the territories and Bernie won the Democrats Abroad. Of the states that were not tested almost all went to Bernie.

Hillary Clinton:

Of the 38 states I tested Hillary performed worse in the polls in 8 cases. Of those 8, she performed way worse in 5 of those states and slightly worse in 1. Hillary Clinton performed better than the polls in 19 states. Of those 18 she performed way better in 8 and slightly better in 3. She performed about what the polls were showing in 11 states.

The polls in Hillary's case actually undersold her performances rather than the other way as had been suggested throughout the primaries.

Bernie Sanders:

Of the 38 states Sanders did worse than the polls in six cases. He performed way worse in two states and slightly worse in two as well. He did better in 21 states. Of those 21 states he did way better in 11 states and slightly better in 1 state. Like Clinton, he performed about as expected (poll wise) in 11 states.

Sanders and Clinton performed about the same in the polls. They both performed about the way the polls were showing in 11 states and they both over performed more than they under performed.

Results:

The problem with this primary season as far as the polls are concerned is not that the polls did not do well, it completely mattered how much polling was done.

If barely any polling was performed the polls did not predict the outcome very well. If there was a good amount of polling the polls were very good predictors of how the elections came out.

In almost every single case, the last poll performed before the elections were way off one way or the other.