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Statistician on why Washington is weird

Post by John Henrikson / The News Tribune on Oct. 13, 2010 at 1:07 pm |
October 13, 2010 1:37 pm

Writing on his New York Times’ FiveThirtyEight blog, number cruncher Nate Silver has an interesting take on the wildly divergent poll numbers coming out of our state on the nationally watched Patty Murray/Dino Rossi race.

As anyone who reads Political Buzz day-to-day knows, it’s hard to get a bead on where this race stand. Several recent polls have indicated a statistical dead heat, but then comes yesterday’s Elway poll showing Murray up 15 points. It’s not unusual for polls to vary on certain races, but Silver points out that pollsters have been perennially off the mark in predicting election day outcomes for Washington state.

What gives? Silver has no definitive answers, but some educated guesses:

One reason could be that it is one of two states, along with Oregon, where voting takes place almost entirely by mail. This can wreak havoc with traditional likely voter models, which often ask questions like, “Have you voted in the election precinct before?” and “Do you know where people in neighborhood go to vote?” — questions that are nonsensical in the context of an election that takes place by post. Also — probably because of mail balloting — turnout in Washington and Oregon has generally been very high, so targets that might work well in other states could fail there. Finally, since many voters in Washington return their ballots well in advance of Election Day, a pollster surveying the race close to Election Day will encounter another type of voter — those who claim to have voted already — which traditional likely voter models are not well designed to handle.

He also adds:

A few other things about Washington State are worth considering. First, Washington, a technologically savvy state, has a somewhat higher than usual number of cellphone-only adults, which pollsters may not be capturing. It also has a fair number of Asian-American voters, who can sometimes be hard to reach because of language or cultural barriers. These things could make a difference at the margins.

What are we to draw from this as it relates to Rossi-Murray?

In the absence of any other information, the thing you usually do when polls diverge is simply to average them and hope for the best. There is a special reason to do so in this case, since the polling firms that show the outlying results have some history of being biased in the same directions that they are now: Rasmussen and SurveyUSA, too favorable to Republicans; Elway, a bit optimistic for Democrats.

That would point toward Ms. Murray indeed holding a small lead, one that could be somewhat more meaningful than usual given that many ballots in Washington are sent in before Election Day and it is hard to make up ground late — although Mr. Rossi obviously retains decent chances.

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