Friday, September 17, 2004
It boils down to the partisan composition of each poll's sample, says Teixera. According to his analysis, the latest Gallup and New York Times polls (showing Bush with sizable leads) oversample Republicans.
On the other hand, the recent Democracy Corps, Pew Research Center and Harris polls (all showing an even race) surveyed a more representative group of voters, he argues:
The Gallup internals show Kerry with a 7 point lead among independent RVs. Huh? Kerry's losing by 8 points overall, yet leading among independents by 7. How is that possible? Only if there are substantially more Republicans than Democrats in the sample.
That suggests that reweighting the sample to reflect the 2000 exit poll distribution (39D/35R/26I) would give a different result. It does: the race then becomes dead-even, instead of an 8 point Bush lead. (Note: Steve Soto of The Left Coaster got Gallup to give him their party ID distributions for this poll and confirms a 5 point Republican party ID advantage in their RV sample.)
One final note: I mentioned the Pew Research Center poll had the race dead-even just like the reweighted Gallup data. And what was Pew's party ID distribution in their RV sample? You guessed it: a 4 point lead (37-33) for the Democrats, just like in the 2000 exits.