The Rasmussen effect
Mon June 7, 2010 6:39 am

There has been considerable discussion on this site about the accuracy of Rasmussen polls, particularly in the Kentucky Senate race. Rasmussen had Rand Paul +25 over Democrat Jack Conway. This was a significant outlier.

Last week pollster.com had an article about Rasmussen polls, which I am going to reproduce here, with some editing. Rasmussen polls the Texas governor's race every two months, so its accuracy--or lack of it--is a crucial factor in reporting about that race.

The gist of the criticism of Rasmussen is this: Rasmussen has a Republican "house effect." He produces polls like the Rand Paul - Jack Conway poll in Kentucky that supports a "Democrats are doomed" theme. Then he brings his poll back into line with others, and the "real" polls, which are generally pretty accurate, come out right before the election.

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Here is the pollster.com article. The author is Harry Enten:

I am going to state the obvious: Rasmussen has had more favorable horse race numbers for Republicans this cycle than other pollsters. Why? It could have to do with its likely voter screen, interactive voice response technology, or perhaps, as some have suggested, a more sinister motive to "shape the debate". But something funny has happened in the past four days, Rasmussen's numbers have come back in line in three states.

Indeed, Rasmussen has released polling data that seems to show a Democratic uprising in Rasmussen's polling. In the state of Kentucky, Jack Conway has, in less than two weeks, cut Rand Paul's post-primary lead from 25 (on the prior Rasmussen poll) to 9. In Connecticut, Dick Blumenthal has seen his lead over Linda McMahon grow from 3 to 23 on Rasmussen polling in less than two weeks. Finally, in Missouri, Roy Blunt's 5+ point lead seen in every Rasmussen poll since February has dropped to a statistically insignificant point.

In the case of the first two contests, the shifts are exaggerated because the previous poll done by Rasmussen was fielded in one night less than 24 hours after two very important events: the first New York Times story on Blumenthal's war record on May 17 and Rand Paul winning the Kentucky primary on May 18. However, a Greenberg Quinlan Rosner poll showed a 15% Blumenthal lead over almost the identical field period as Rasmussen's 3 point Blumenthal advantage poll. While Rasmussen polls in Connecticut and Kentucky taken before these outliers were not as "out there", there was still a Republican house effect in these states and Missouri .

Interestingly, these more friendly Democratic numbers remind me of something that happened during the 2008 election. My friend David Shor, who I am currently working on projects with, documented that Rasmussen had a "summer" reversal of its Republican house effect in 2008. Looking at all polling from presidential, senatorial, gubernatorial, and house races, David found "Rasmussen polls have a statistically significant Pro-Republican house-effect that appears during primary season in the beginning of the year, disappears during the summer, and then very rapidly appears right before the Republican National Convention." [chart omitted]

Here is what the liberal Web site Daily Kos has to say:

Yesterday [May 18] the nation had several hot races, including the House special election in PA-12, primaries in both parties in Kentucky and Arkansas, and the Democratic Senate primary in Pennsylvania.

And somehow, Rasmussen was nowhere to be found. Yet this past week, Rasmussen found time to poll Colorado, California, and those burning Idaho senate and governor races. He even polled the general election in Arkansas, ignoring the imminent primaries -- the better to show Arkansas Republican primary voters who their strongest candidate was.

You see, the thing about Rasmussen is that he cares only about setting the narrative that Democrats are doomed. And it's hard to build those narratives if you screw up polling actual elections.

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I'm not going to take a position on whether Rasmussen's polls are designed to support a "Democrats are doomed" narrative. You could read the last two Rasmussen polls in the governor's race (Perry +4, Perry +13) as supporting the "D.A.D." narrative. Then bloggers like me write, oh, yes, the Democrats are doomed. (As I think they are.) But Rasmussen polls bear close watching, at the very least, and I suggest that we keep on hand a large supply of Morton's iodized salt.

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