The Wild Differences in The Polls, Explained

By Andrew Satter,
CQ Staff

If you’ve been watching Presidential preference polls over the past week, you might feel a bit whipsawed.

For the second straight day, Gallup’s daily tracking poll Thursday has John McCain and Barack Obama tied. Both candidates dropped a point from yesterday’s tracking poll, down to 44 percent. The margin of error is +/- 2 percentage points.

The Rasmussen daily tracking poll in the same period of time has shown a 3-7 point gap between the two candidates.

Neither of the daily tracking polls square with two polls from that show Barack Obama holding a stunning double-digit lead. A Los Angeles Times/Bloomberg poll showed Obama with a 12 point lead over McCain, and a Newsweek poll had Obama leading by 15 points, if Ralph Nader and Bob Barr were included in the mix.

Why the difference? Were the Newsweek and L.A. Times biased in favor of Obama? Do the Rasmussen and Gallup pollsters favor McCain? Or maybe the public is wildly changing its views, daily.

All unlikely, says Richard Morin, a senior editor at the Pew Research Center. In an interview with CQ Politics, he said the discrepancy is probably a result of the Newsweek and L.A. Times/Bloomberg polls over-representing Democrats.

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