I seem to be failing in my resolution after the last election to ignore the major media polls. So to try to channel that wasted nervous energy into something moderately productive, I decided yesterday to take a look at how the major polls did in the last couple Presidential elections.
In 2000, the polls in the last two weeks prior to election day ranged from a tiny lead for Gore (+2, Zogby & CBS) to a large lead for Bush (+9-13, Rasmussen, Gallup). Most were in between, showing Bush with a 2-5 point lead. The final result was at the extreme end of that range, of course, with Gore winning by half a percent.
In 1996, the final polls ranged from a Clinton blowout (+18, CBS/NYTimes) to a much more modest victory (+8, Zogby). Again, most were in between. And again, the final result was at the extreme end of that range, as Clinton won by 8.
What lessons do we take from this? Trust Zogby, since he got it right both times? Or simply pick an extreme end of the polling range (e.g., large victory for Bush or modest but decisive victory for Kerry)?
Zogby is certainly worthy of paying close attention to given his track record nationally. But part of his success in the last two Presidential elections was due to luck, since statistical variation alone could cause him to miss the margin by 3-4 points, and that hasn't happened yet. (In 1996 he was dead on, and he was off by 1.5 points in 2000.)
The real lesson, in my opinion, is to simply not trust the polls unless they indicate a very large lead (over 10 points) for one candidate, and even then don't trust the actual margin. In 1996 and 2000, when taken as a whole, the major polls were significantly biased---by 4-5 points in one direction or the other: in 1996 towards Clinton; in 2000 towards Bush. I strongly suspect they are still biased by a similar amount. Perhaps even worse, since by all reports there will be many more new voters than usual in this election.
In which direction is the bias?
I have a good feeling about the answer to that one.
Comments