September 25, 2007

On Plouffe's Memo and the Disclosure Project

A public memo circulated today by the Obama campaign and authored by campaign manager David Plouffe (via Marc Ambinder) argues that "Iowa is fundamentally a close three-way race with Obama, Clinton and Edwards all within the same range in most public polling." His characterization is reasonable, especially if one defines that "same range" as roughly seven percentage points wide. Our own trend estimates for Iowa based on all available public polls show both Clinton and Edwards running a few points apart in the mid twenties (Clinton does slightly worse and Edwards slightly better if we exclude the polls by the American Research Group) with Obama trailing at roughly 20%.

But Plouffe goes on to make an assertion that is harder to evaluate:

[P]olls consistently under-represent in Iowa, and elsewhere, the strength of Barack's support among younger voters for at least three reasons. In more than one survey, Barack's support among Iowa young voters exceeded the support of all the other candidates combined. First, young voters are dramatically less likely to have caucused or voted regularly in primaries in the past, so pollsters heavily under-represent them. Second, young voters are more mobile and are much less likely to be at home in the early evening and thus less likely to be interviewed in any survey. Third, young voters are much less likely to have a landline phone and much more likely to rely exclusively upon cell phones, which are automatically excluded from phone surveys. So all of these state and national surveys have and will continue to under-represent Barack's core support – in effect, his hidden vote in each of these pivotal early states. Of course, there are organizational challenges associated with maximizing this support, but we are heavily focused on that task.

Each of the Plouffe's three arguments is at least theoretically plausible, particularly in Iowa, but hard to prove or disprove conclusively with the data available.

Consider the cell phone effect. We know that younger adults are much more likely to live in cell-phone only households, that unweighted national poll samples tend to skew older as a result but that age-related bias tends to fade to just a percentage point or two (at most) when pollsters adjust their adult samples to match census age estimates. However, in a state like Iowa, the big polling challenge is to select the "likely caucus goers" that will hopefully represent the tiny sliver of adults that will choose to participate in the caucus. The “census norms” available for all adults are of much less utility when trying to determine the appropriate demographic composition of the one-in-ten voters that we hope will represent likely caucus-goers.

Pollsters will argue and disagree among themselves about the best way to model and weight likely voters in a state like Iowa. We will not be able to resolve those arguments here. What the rest of us should be looking for, at least, is whether the various public polls are showing variation in their age composition and whether any such variation is making a tangible difference in the results.

Although Plouffe may be cherry-picking an unusally favorable result, the national surveys consistently show Obama doing better among younger voters. For example, in a combined crosstabulation of its five most recent national polls (conducted since June), the Cook Political Report/RT Strategies survey shows Obama receiving 30% of the vote among 18-24 year olds, 24% among 25 to 49 year olds and only 17% among those over 50. So if early state polls are under representing younger voters, they may be slightly understating Obama's support.

But how much is the age difference in Iowa and how much do the Iowa polls (or any of the other early states) vary by vary in their age composition? Who knows? As far as I can tell, only the Time survey conducted by in late August has reported its composition by age and other demographics.

All of which brings me back to the Pollster.com disclosure project. One of the most important reasons why we are requesting additional details on the polls conducted in Iowa and the other early states is to allow us all to better evaluate arguments like the one Obama's campaign manager made today. So please read my post from earlier today and comment or blog if you think this is a worthy idea. We would appreciate your support.

-- Mark Blumenthal

September 25, 2007 in Disclosure, The 2008 Race

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