The results from a number of state polls from the industrial mid-west and Pennsylvania conducted by the Big Ten Battleground Poll and released over the past 24 hours were incredibly favorable for Barack Obama. Their polling gave Obama a 22 percentage point lead in Michigan, a 19 point lead in Minnesota, a 12 point lead in Ohio and a really eye-opening 10 point lead in Indiana. As I will show shortly in another post, a 12 point lead in Ohio suggests that Obama is, more or less, up by about 12 percentage points nationally. The results from an Ohio state poll conducted by Quinnipiac University gives Obama and even bigger 14 point lead in Ohio suggesting that a national lead of about 14 points for Obama. The overall sense is that Obama's lead is now growing by leaps.
The problem is that a weighted average of the national tracking polls gives Obama about a 7 percentage point lead over McCain and that McCain has actually gained slightly on Obama over the past 24 hours. The difference between the national tracking polls and these state polls is not just a matter of statistical uncertainty since the Big Ten and Quinnipiac polls are internally consistent across states. Rather, such polling results (and those conducted by other polling organizations) may well be the result of some type of bias. If the reader is interested in this issue, this AP article gives an overview of what type of biases may produce this result.
My model has been designed to deal with isolated polls of dubious quality, since such polls tend to average out in the wash giving, in the end, a reasonable outcome. However, a flood of such polls as noted above is a completely different issue. To deal with this problem, I have decided to strip out polls from organizations other than major professional polling organizations like Gallup, Rasmussen, SurveyUSA and Research 2000. This will take a bit of time and I may not be able to get the revised results out until later in the day. I have checked out the results using only the national tracking models. There is a very slight reduction in Obama's lead, but it does not appear at this time that any significant change has been made compared with yesterday.