I was just looking through the very last polls before Pennsylvania to see which one got it right. It looks like they pretty much all got it right.
I was just looking through the very last polls before Pennsylvania to see which one got it right. It looks like they pretty much all got it right. Any differences seem to have been completely explained by the number of undecided voters. I took each of the polls in RCP's latest average and applied the undecideds at a regular margin. I used the split from CNN's exit polls for those who decided on the day of the primary (11% of the total): 59-41 in favor of Clinton. Note also that this is about what people were predicting before the election (and is about how voters who decided in the last three days split as well).
The average of the adjusted numbers is: 53.7 - 46.3. The actual total looks to be around 54.7 - 45.3 (again, CNN). What's more if you throw out the PPP poll which was the only one to show Obama winning and the only one to show Obama polling higher than 44% (yet with still 7% undecided), the average is 54.23 - 45.77. That's pretty close to what we ended up with.
Also, if you look at each individual pollster, none was more than 1.5 points off this adjusted average (as well as the final tally), and most were within 1 point (PPP aside). I'm not gonna go back and see how this kind of analysis holds up in the other primaries, but I'd say by this point we've got a pretty solid hold on the demographic voting habits and likely voter screens (despite some of the handwringing about turnout models) this year and I would bet that the polls, on average, are getting more accurate.
I think the upshot of all of this is that it is aiding the stagnation of this race. A 9/10 point win for Hillary is probably the exact result to change exactly nothing. But is this a coincidence? I think the expectations (and the expectations were pretty easy to pin down given the consistency of these polls) drove the supposed conventional wisdom which said if it was in the high single digits, she could justify going on but that she wouldn't really have gained anything tangible. But that seems like the tail wagging the dog, right?
cross posted at my blog