In reading Professor Larry Jacobs’ defense of the Hubert H. Humphrey Institute poll – which always underpolls Republicans in its immediate pre-election survey, by an average of six points, with the tendency even more exaggerated in close races – Jacobs writes (with emphasis added):

Appropriately interpreting Minnesota polls as a snapshot is especially important because President Barack Obama’s visit on October 23rd very likely created what turned out to be a temporary surge for Dayton. Obama’s visit occurred in the middle of the interviewing for the MPR/HHH poll; it was the only survey in the field when the President spoke on October 23rd at a rally widely covered by the press. Our write-up of the MPR/HHH poll emphasized that the President appeared to substantially increase support for Dayton and suggested that this bump might last or might fade to produce a closer race:

Well.  That kinda covers all the possibilities, doesn’t it?

Effect of Obama Visit: Obama’s visit to Minnesota on October 23rd and the resulting press coverage did increase support for Dayton. Among the 379 likely Minnesota voters who were surveyed on October 21st and 22nd (the 2 days before Obama’s visit), 40% support Dayton. By contrast, among the 145 likely Minnesota voters who were surveyed on October 24th and 25th (the 2 days after Obama’s visit) 53% support Dayton. This increase in support for Dayton could be a trend that will hold until Election Day, or it could be a temporary blip that will dissipate in the final days of the campaign and perhaps diminish his support.

Did you catch that?

Obama’s presence in the city caused Daytons’ numbers to boom by five points (if you take the HHH’s numbers at face value, something no well-informed person ever does), and then lurch downward by a dozen by election day?  The presence or absence of Barack Obama is responsible for one out of eight Minnesota voters changing their mind and changing it back inside of a week?

Obama’s impact in temporarily inflating Dayton’s lead is a vivid illustration of the importance of using polls as a snapshot.

No.  The HHH polls’ impact in temporarily inflating Dayton’s lead is vivid illustraiton of how these polls need to disregarded or abandoned!.

Indeed, according to the MPR/HHH poll, Dayton’s lead before Obama’s visit was 8 points – nearly identical to the Star Tribune’s lead at nearly the same point in time (7 points). Treating polls as snapshots, then, is especially important when a major event may artificially impact a poll’s results or, as in the case of the MPR/HHH poll, there were a large number of voters who were undecided (about 1 out of 6 voters) or were considering the possibility of shifting from a third party candidate to the Democratic or Republican candidate.

Read another way:  “They’re snapshots, so we can’t be held accountable.  But keep the funding and recognition coming anyway”.

The take-home point: polls are only a snapshot of what can be a fast moving campaign as events intervene and voters reach final decisions. Polls conducted closest to Election Day are most likely to approximate the actual vote tally precisely because they are capturing the changing decisions of actual voters.

Newport dipolmatically notes the real “take-home point”:

The authors raise the issue of the impact of President Obama’s visit to Minnesota on October 23rd. The authors note, and apparently reported when the poll was released, that interviews conducted October 24th and 25th as part of the MPR/HHH poll were more Democratic in voting intention than those conducted before the Obama visit. It is certainly true that “real world” events can affect the voting intentions of the electorate. In this instance, if the voting intentions of Minnesota voters were affected by the President’s visit, the effect would apparently have been short‐lived, given the final outcome of voting. The authors do not mention that the SurveyUSA poll also overlapped the Obama visit by at least one day. It is unclear from the report if there is other internal evidence in the survey that could be used to shed light on the Obama visit, including Obama job approval and 2008 presidential voting.

Up next – at noon – what effect do bogus polls really have on voters?