How To Look At Polls
By Big Tent Democrat
Speaking for me only
Having derided polls (mostly because they over claim their value, particularly when omitting how fragile their likely voter models are) for most of my time blogging, I find my intense interest in them in this election contest rather perverse. But I think there is a good reason for my interest. The polls have produced data worth considering when taken in conjunction with the exit polls. The reason is that demographics have completely driven this contest. But what can we make of polls that show such wide divergences between each other? I think a lot. I'll explain why on the flip.
Unlike most any contest I have seen, in this year's Dem contest, if we know the demographics we pretty much know the result. This is especially so in the big contested states. Demography has been political destiny.
So when we look at the SUSA PA poll, which has Clinton up 18, and compare it to the just released PPP poll, which has Clinton now up 3 (previously PPP had Obama up 2), I think we can see why and make judgments on the data presented.
PPP writes:
Clinton has a 46-43 advantage in the state after trailing Obama by two points in PPP’s poll last week. Clinton’s improvement since last week comes almost entirely from her core demographics. Her lead among women improved from 10 points to 16, her lead among white voters went from 11 to 17, and her lead with senior citizens showed a gain from 16 to 21.
By contrast, SUSA has Clinton winning whites by 61-32, seniors by 65-29 and women by 61-33. SUSA expects whites to be 82% of the electorate (PPP does not tell us what it expects the demographic breakdown to be) and women to be 58% of the electorate (again PPP is silent on this.) The undecided in SUSA is 6 points. In PPP, it is 11. That is not the explanation for these differences. While PPP does not tell us, I suspect they have Obama doing much better with A-As than does SUSA which has Obama winning "only" 75% of the black vote.
We can project PPP's findings (I will assume an 85-15 split in the A-A vote) using the SUSA turnout model. Let's assume, using PPP's numbers, whites go 59-41 for Clinton X 0.82(SUSA's assumed white percentage of the turnout), that is 48-4%, plus 0.15 (I assume Obama winning A-As by 85-15) X 0.14 (SUSA's assumed A-A percentage of the turnout), that's 2 percent, plus 2 percent of the remaining 4 percent of the vote.
That means the PPP result using SUSA voter turnout models will show a Clinton 5 point win in PA, 52.5 to 47.5.
SUSA, contrary to PPP's prediction of Obama capturing 41% of the white vote, predicts Obama capturing about a third of the white vote. If we extrapolate the undecided whites we have Clinton winning 66% to Obama's 34%. We do the math as described above and that is 54%. I adjust Clinton's percentage of the A-A vote down to 15% from SUSA's 24%, and add another 2% to Clinton and 2% of the remaining 4% and that gives me Clinton 58%, Obama 42%.
So who will be right? I do not know, but I think PA is more like Ohio than Missouri. And PA is certainly not Wisconsin. It seems impossible to me to see how Obama can beat Clinton in Pennsylvania. The question is by how much. I think Obama's best case is a 5 point loss. Worst case? As much as 20. Demography is destiny in Pennsylvania.
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