The Wild Differences in The Polls, Explained

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.

"When I look at those results, I know something is going on," said Morin. "The first place that I look when I see these discrepancies, I look for the percentage of Republicans, Democrats and Independents in the sample. We know that the best predictor of how someone is going to vote is their party ID. "Both the L.A. Times/Bloomberg and the Newsweek polls have (too) large percentage of Democrats and a (too) small percentage of Republicans." While there are indeed more people who identify themselves as Democrats than Republicans in the country, Morin says the other polls, including Gallup, are more in line with the actual disparity than the Bloomberg or Newsweek polls.

"Interestingly enough," Morin said, "if you do the math and apply the proper percentages to the L.A. Times/Bloomberg and the Newsweek findings, you find that their results change dramatically." In fact, Morin says, if the two polls that show Obama winning by a large margin were to modify their findings using the same percentage of Democrats and Republicans as other polls, Obama's lead would come down to somewhere between a toss-up and a small, single digit lead for Obama.

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Posted by John Ray. For a daily critique of Leftist activities, see DISSECTING LEFTISM. For a daily survey of Australian politics, see AUSTRALIAN POLITICS Also, don't forget your roundup of Obama news and commentary at OBAMA WATCH