Saturday, October 30, 2010 at 11:42 am by Darryl
A new Marist poll has been released in the race between Sen. Patty Murray (D-WA) and real estate wheeler-dealer Dino Rossi (R).
The poll of 638 likely voters (4.0% MOE) taken from 26-28 October has Murray leading Rossi 49% to 48%. Marist polls use live interviews and include a sub-sample of cell phone interviews. As we saw with the Marist poll from two weeks ago that had Murray up by +1%, the current poll is evidence against the otherwise strong trend of live-interview polls showing a modest (or better) lead for Murray.
I ran a Monte Carlo analysis that simulated a million elections using the observed preferences and sample size percentages observed in the new Marist poll. Murray won 567,112 elections and Rossi won 422,059 times. The poll (by itself) offers evidence that Murray would win with an election held over the past two weeks with a probability of 57.3%. Rossi would have a 42.7% probability of winning. Clearly, this result is a statistical tie, even if Murray’s odds are a bit better than Rossi’s.
With today’s poll, we have now had seven polls released that cover the past two weeks. Murray has led in five of the polls, Rossi has led in one, and one was a tie. A combined analysis of all seven polls provides a way to use all the recent evidence to assess this race. The resulting meta-poll had a total of 5,778 “votes” of which 2,797 go to Murray (48.4%) and 2,712 go to Rossi (46.9%). An additional 269 (4.7%) “votes” went to neither candidate.
The Monte Carlo analysis gives Murray 789,523 wins to Rossi’s 207,597 times. Thus these seven polls provide evidence that Murray would win an election held over the past two weeks with a probability of 79.2%. Rossi would win with a 20.8% probability.
With only three days to go until the Big Poll is tallied, it is worth a few minutes examining the recent trend in this race. Here is the collection of polls in September and October (I’ve excluded polls released by a candidate or party):
The very recent polling suggests a tightening race. Even so, Rossi has only led in three of 19 polls over the past two months, and all three were conducted by Rasmussen (and Murray has led in two other Rasmussen polls). Beyond that, Murray has led in all other polls conducted by seven other pollsters except for one of three SurveyUSA polls giving a tie.
The bottom line is that Murray looks like she will win this one, but there are some uncertainties that may be distorting the map between polling and actual voting. My hunch is that the uncertainties don’t help Rossi’s chances much and some favor Murray:
- Voter “turnout.” There really isn’t “turnout” in Washington, which has a very high proportion votes cast by mail-in ballots. Voter motivation should be less of an issue in this race than it will be in other states. You may have heard media reports about how a rainy day across the country on Tuesday will negatively affect Democratic candidates. While that may be true in states with poll voting, rain in Washington state can potentially give Democrats a boost by simply keeping inattentive voters in closer proximity to their unspent ballots.
- The “cell phone problem.” There wasn’t much evidence that this problem biased polls in 2008, but there is some more recent evidence to suggest it can now. Some pollsters, like Marist, include a cell phone sub-sample, but it is hard to do. If the phenomenon is real, Murray will do better than many polls suggest.
- The robopoll—live interview difference. I’ve been discussing this for weeks after Stuart Elway first raised it. The phenomena is observed nationally as well as in this race. Here, I suspect it will result in a 3%-4% boost for Murray over the robopolls, but nobody really knows what is causing the phenomenon. We’ll find out soon.