Wednesday, October 6, 2010

Who's polling The Minnesota Governors race

Only four pollsters; Rasmussen, SurveyUSA, Princeton Survey Research Associates (PSRA) and Humphrey Institute, have polled the Minnesota Governors race this year and with under a month left before the election it's unlikely that many more will jump in. In 2006 these same four pollsters (StarTribune had in-house polling in 2006, now they contract with PSRA) were joined by Mason-Dixon, St. Cloud St. and Polimetrix, so it's possible that one of them or someone else entirely will drop a poll on us but for now we're just going to look at who's been polling it so far.

A few notes on terms and formatting first.

PIE is Pollster Induced Error, a metric developed by Nate Silver, it's a measure of how much error, above average, a pollster contributes based on an analysis of past polls.

Past election results are listed as follows:
Race Polled: Last polling result (Actual results) Margin Difference
The margin difference is the polling margin minus the actual margin.

When looking at the past election results one thing to keep in mind is that no one got the 2006 Governor's race correct, there was not a single poll that showed Tim Pawlenty ahead of Mike Hatch in the last month of the election. Out of the nine polls done in the last month only one showed a tie, the rest showed a Hatch lead of between 1 and 9 points.

Doing a simple average of all the polls in the last month gives us a result of 45.5 Hatch, 42.5 Pawlenty, which is very close to Hatch's final numbers but missed Pawlenty's by about 4 points. This is likely due to late breaking events that were particular to that race and that caused undecideds to break for Pawlenty in the last week, whereas in a normal race you would expect a more equitable distribution of the undecided vote.

In the other two races listed, the 2006 and 2008 Senate contests, a simple polling average provides a very good indicator of the final results, showing the 2006 Senate race at 55-37 (actual 58-38) and the 2008 Senate race at 39-39 (actual 42-42).

PIE: 1.74
Minnesota polling history:
2006 Gov: 47D/45R (46D/47R) 3D
2006 Sen: 54D/40R (58D/38R) 6R
2008 Sen: 39D/43R (42D/42R) 4R

Rasmussen, run by Scott Rasmussen, is by far the most prolific public pollster in the business today. This is no doubt due to how they conduct their polls; in a one night only, automated blitz fashion. Whereas most pollsters will conduct a poll over the course of a few days, Rasmussen usually just does one night, because of this if someone isn't home they don't call back, they just move on to the next number. They also don't try to randomize who they talk to, instead being content just talking to whoever answers the phone. Additionally Rasmussen has a reputation as being a Republican leaning pollster, yet despite all of this they are rated as above average according to Nate's analysis.

Client: KSTP-TV
PIE: 1.19
Minnesota polling history:
2006 Gov: 45D/45R (46D/47R) 1D
2006 Sen: 56D/40R (58D/38R) 4R
2008 Sen: 39D/44R (42D/42R) 5R

SurveyUSA is run by Jay Leve and is one of the larger pollsters in the country. Like Rasmussen they are an automated pollster, although they don't employ the blitz approach that Rasmussen does. They were the subject of a post of mine earlier in the week and have had sometimes sketchy results this cycle, at least compared to other pollsters, although they have a good history of accuracy sporting the best PIE of the four. They are not really considered to be a Republican or Democratic leaning pollster although their numbers have skewed to the GOP this cycle.

Princeton Survey Research Associates (PSRA)
Client: StarTribune
PIE: 1.81
Minnesota polling history:
2008 Sen: 42D/38R (42D/42R) 4D

In 1989 Andrew Kohut, along with some of his colleagues, left Gallup to found PSRA. Kohut is now the head of Pew Research, but PSRA is still around and is now run by Larry Hugick. Unlike Rasmussen and SUSA, PSRA is not an automated pollster, they are an old fashioned live operator pollster. PSRA took over polling duties for the StarTribune after the 2006 election.

Humphrey Institute
Client: MPR
PIE: 3.15
Minnesota past history:
2006 Gov: 45D/39R (46D/47R) 7D
2006 Sen: 55D/33R (58D/38R) 2D
2008 Sen: 41D/37R (42D/42R) 4D

Larry Jacobs is in charge of the public opinion polling done by The Humphrey Institute and like PSRA they do live operator polling. However, they have the worst PIE score of the four pollsters and as pointed out in numerous other posts by myself and others, they always have partisan id numbers that make you scratch your head.

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