GPI update; Horner's slide continues

Rasmussen (10/22, likely voters, 10/6 in parentheses):

Mark Dayton (D): 44 (40)
Tom Emmer (R): 41 (38)
Tom Horner (I): 10 (15)
Undecided: 4 (5)
(MoE: ±4%)

This is the third poll in a row to show Mark Dayton with a 2-4 point lead over Tom Emmer and Tom Horner losing support since the last poll by the same pollster, although by a much more significant margin than we've previously seen. Despite what I wrote yesterday, there is now reason to believe that Tom Horner's support is in fact eroding, similar to what happened to Tim Penny in 2002, although I would certainly like to see another poll showing him this low before jumping to any conclusions.

GPI update; Ras now says no to leaners

Rasmussen (10/6, likely voters, 9/22 in parentheses):

Mark Dayton (D): 40 (34)
Tom Emmer (R): 38 (36)
Tom Horner (I): 15 (18)
Undecided: 5 (2)
(MoE: ±4%)

A few things change with this update of the GPI, the first of which is something truly radical, standardizing the way I format new poll results. I put a lot of thought into what the most effective way to do it would be and after careful deliberation I decided to crib Swing State Project's poll formatting style, so if it looks familiar you know who to blame.

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.