Polls, Damned Polls, and Lies

I hate to turn to sources as partisan as the Huffington Post for my news -- I usually swing by for a daily chuckle (or grimace) -- but Seth Colter Walls' piece today shines a light on the recent spate of polls, and how they differ from an earlier batch.

Two things: a higher sampling of Republican leaners and the possible undercounting of newly registered voters. Colter explains:

This week's mainstream coverage of the presidential horse-race has been dominated by a series of polls showing the McCain-Palin ticket with its first stable lead over Obama and Biden. Gallup's tracking poll, USA Today and CBS News all show the Republicans with some kind of lead over the Democratic ticket. But, interestingly, all three polls were also conducted using a higher sampling of Republican voters than in July, thus raising a question of methodology.

In a year in which Democrats have a lead of 11 million registered-voters over Republicans, and have been adding to that advantage through a robust field operation, are pollsters over-sampling Republicans?

I'd been wondering something similar this week, though I hadn't actually wondered hard enough to do any research or reporting on it.

Emory University political scientist Alan Abramowitz is highly skeptical of the new Gallup, USA Today and CBS polls. About the latter, which showed a statistically insignificant two point lead for McCain, Abramowitz said: "One reason for the dramatic difference between the two recent CBS polls is that the two samples differed fairly dramatically in terms of partisan composition. The first sample was 35.2% Democratic, 26.2 percent Republicans, and 38.6 percent independent. The second sample was 34.9% Democratic, 31.1% Republican, and 34.0% independent. That's a change from a 9 point Democratic advantage to a 3.8 point Democratic advantage. That alone would probably explain about half of the difference in candidate preferences between the two [CBS] polls."

Message: Read the fine print.