Reading between the (poll) lines

Why Rasmussen's numbers look different

Over the last month or so, we have seen a steady stream of new polling data in the Massachusetts gubernatorial election. In reading these polls, there seem to be two different assessments of the election. Scott Rasmussen shows Gov. Deval Patrick with a 47-42 lead over Republican Charlie Baker, with independent Tim Cahill drawing a scant 6 percent, his support having fallen recently. Other pollsters show Patrick and Baker each holding just about steady in the mid-to-high thirties, with Cahill stable in the low double digits (see graphics). What is going on here?

All pollsters except Rasmussen


Rasmussen polls only

The short answer is that Rasmussen includes a group that he calls “leaners” in his current horserace calculation. I add the quotation marks because his definition of leaners is unconventional. While most, if not all, pollsters include leaners in their polling data, the usual definition is different from Rasmussen’s. To clarify these differences, I obtained confirmation from Rasmussen himself that my understanding of his methodology is correct.

A conventional definition of “leaner” can be found on NORC’s website.

A survey respondent who does not make a choice among alternatives in an initial question, but makes a choice once asked if he or she leans toward one of the alternatives.

In Rasmussen’s case, he includes another group in his definition of leaners.  This extra group of leaners includes those who initially say they are voting for someone other than the Democrat or Republican, but who are uncertain of their vote.  This includes both those who say they are voting for “some other candidate” as well as those who say they are planning to vote for Cahill.  So, for example, if a respondent says she is voting for Tim Cahill in the initial horserace question, but that she is uncertain of her choice, she will get a followup “leaner” question.

Respondents will not, however, get this same “leaners” question if they say they are supporting Patrick or Baker in the initial horserace question.  For this reason, when compared to the basic horserace, Cahill’s numbers drop when “leaners” are included and Patrick’s and Baker’s numbers rise.  This calculation accounts for why both Baker and Patrick appear to be drawing more support overall with Rasmussen when compared to other pollsters. 

Cahill’s recent downward trend in Rasmussen’s data is also an artifact of another aspect of this methodology.  Rasmussen reports the race without “leaners” before Labor Day and “with leaners” after Labor Day.  When this change was made last month, Cahill’s support appeared to drop suddenly, whereas other pollsters are showing Cahill’s support having leveled out recently. 

It may turn out that Rasmussen is correct in pegging the final support that will go to Cahill.  As Rasmussen writes, their approach toward leaners “anticipates that support for third party candidates typically declines as Election Day nears and voters begin to gravitate toward one of the major party nominees.” Perhaps he is right. 

Meet the Author

Steve Koczela

President, MassINC Polling Group

About Steve Koczela

Steve Koczela is the President of The MassINC Polling Group, where he has grown the organization from its infancy to a nationally known and respected polling provider. During the 2014 election cycle, MPG conducted election polling for WBUR, the continuation of a three-year partnership. Koczela again led the endeavor, producing polls which came within one point of the margin in both the Massachusetts gubernatorial and U.S. Senate Elections. He was also lead writer for Poll Vault, WBUR’s political reporting section during the 2014 Election Cycle.

He has led survey research programs for the U.S. Department of State in Iraq, in key states for President Barack Obama’s 2008 campaign, and has conducted surveys and polls on behalf of many private corporations. Koczela brings a deep understanding of the foundations of public opinion and a wide ranging methodological expertise. He earned U.S. Department of State recognition for his leading edge work on sample evaluation in post conflict areas using geospatial systems.

Koczela is frequent guest on WBUR as well as many other news and talk programs in Massachusetts and elsewhere. His polling analysis is often cited in local, state, and national media outlets. He currently serves as President of the New England Chapter of the American Association for Public Opinion Research (NEAAPOR). Koczela holds a Master’s degree in Marketing Research from the University of Wisconsin and is a veteran of the war in Iraq.

About Steve Koczela

Steve Koczela is the President of The MassINC Polling Group, where he has grown the organization from its infancy to a nationally known and respected polling provider. During the 2014 election cycle, MPG conducted election polling for WBUR, the continuation of a three-year partnership. Koczela again led the endeavor, producing polls which came within one point of the margin in both the Massachusetts gubernatorial and U.S. Senate Elections. He was also lead writer for Poll Vault, WBUR’s political reporting section during the 2014 Election Cycle.

He has led survey research programs for the U.S. Department of State in Iraq, in key states for President Barack Obama’s 2008 campaign, and has conducted surveys and polls on behalf of many private corporations. Koczela brings a deep understanding of the foundations of public opinion and a wide ranging methodological expertise. He earned U.S. Department of State recognition for his leading edge work on sample evaluation in post conflict areas using geospatial systems.

Koczela is frequent guest on WBUR as well as many other news and talk programs in Massachusetts and elsewhere. His polling analysis is often cited in local, state, and national media outlets. He currently serves as President of the New England Chapter of the American Association for Public Opinion Research (NEAAPOR). Koczela holds a Master’s degree in Marketing Research from the University of Wisconsin and is a veteran of the war in Iraq.

For now, however, this difference in methodology makes it difficult to compare Rasmussen’s polls with those of other pollsters.

Steven Koczela is president of the MassINC Polling Group.