Today, the Louisiana Democratic US Senator Mary Landrieu forwarded via email a link to the article, “Why two Louisiana Senate polls show wildly differing results”. The article was written by Scott Clement. What stands out in the email is perhaps not what was said, but unsaid.
The Landrieu campaign email stated the following:
The polls have numerous methodological differences that may account for the disparity...
...But the polls also differed in what questions they asked respondents before the Senate vote question. The SMOR survey first asked whether respondents had favorable or unfavorable impressions of each Senate candidate, including descriptions of each candidate's residence and occupation. For example, the poll described Cassidy as "a Republican from Baton Rouge who is a medical doctor and U.S. Congressman." The NYT/Kaiser poll preceded election questions with items about the Affordable Care Act and health care -- which could have had their own impact on the results -- but did not provide any description of the candidates before asking the Senate question.
That small biographical cue may have made a difference among an electorate unfamiliar with Cassidy and other Republicans, as barely four in 10 likely voters had any impression of Cassidy in a February likely voter poll. Indeed, the biggest difference between polls was in Cassidy's support, with the Republican garnering 35 percent in the SMOR poll versus just 18 percent in NYT/Kaiser.
So, what was not said in the Landrieu campaign email (but, was mentioned only if one clicked on the link to read the original story)? While acknowledging the polls have “numerous methodological differences”, as noted above, the Landrieu campaign email only refers to one of those differences--the questions asked of the respondents and the identification of the candidates, particularly, describing Cassidy as “a republican from Baton Rouge who is a medical doctor and U.S. Congressman”. Not mentioned in the campaign email was the major difference in the poll-- the SMOR poll was surveyed “likely voters”. By comparison, the NYT/Kaiser polled surveyed adults.
The differences between “Louisiana adults” and “Louisiana likely voters” is significant. In the SMOR poll, Landrieu only led Cassidy 36 percent to 35 percent whereas the New York Times Upshot/Kaiser Family Foundation poll last month. Landrieu led Cassidy by 24 points (42 percent to 18 percent)
Why the Landrieu campaign, in its email, only focused upon the differences in the questions asked is not certain. Not specifically mentioned in the Landrieu email was probably the real difference in the poll--who was being polled. However, Polling Basics 101 would suggest that the “likely voters” criteria would benefit Republicans (especially in Louisiana) in an upcoming election as they, for now, are expected to vote and the Republicans always do better when the poll is of "likely voters". The SMOR poll focused upon "likely voters" for the fall election whereas the NYT/Kaiser poll questioned Louisiana adults, who might or might not even be registered voters.