Are the presidential polls skewed?

[nomoon]

Finding useful articles about the poll skewing situation are hard to come by. The majority of the links which give an anti-skewing argument don’t address the justification for the apparent oversampling of Democrats. The Economist article “Skewed polls, Evil demon” states the following:

Quote:I don't want to spend any time at all explaining why the idea that pollsters overall are deliberately tilting their results in Mr Obama's favour is ridiculous. It's ridiculous, and the fact that a plurality of respondents in a large survey say they believe it to be true is just the latest addition to the colossal pile of evidence showing that we human beings spend our lives inhabiting an ornate palace of self-flattering delusions.

The article then makes three rambling and diffusely defined “points” which cover the bandwagon effect and generalized popular mistrust. The article seemed loaded with generalized smug condescension, but didn’t address the details of a sampling methodology.

There is also a Washington Post also has an article titled “Does the ‘skewed polls’ crowd have a point? Not really.” This article looks a little at public perception of media bias, but avoids all of the specifics of the over sampling issue.

The Atlantic has an article “Are Polls Skewed Too Heavily Against Republicans?” which is better than most, and actually discussed the over sampling issue:

Quote:Critics allege that pollsters are interviewing too many Democrats -- and too few Republicans or independents -- and artificially inflating the Democratic candidates' performance. Pollsters counter that the results they are finding reflect slight changes in public sentiment -- and, moreover, adjusting their polls to match arbitrary party-identification targets would be unscientific.

Unlike race, gender, or age, all demographic traits for which pollsters weight their samples, party identification is considered an attitude that pollsters say they should be measuring. When party identification numbers change, it's an indication of deeper political change that a poll can spot.

"If a pollster weights by party ID, they are substituting their own judgment as to what the electorate is going to look like. It's not scientific," said Doug Schwartz, the director of the Quinnipiac University Polling Institute, which doesn't weight its surveys by party identification.

Since they invoke the work “scientific,” I’ll state that a good scientist would want to use party affiliation data to look at boundary conditions and to make consistency checks. One consistency check that I’d do would be to compare party weighting to party enthusiasm, and to compare these numbers to previous elections. The Atlantic article even mentions these numbers. In 2008, when enthusiasm for Obama was very high, the exit polling show a Democratic turnout of 39%, while Republicans turned out at 32 percent, giving the Democrats a seven point advantage. For the 2004 election (Bush-Kerry), the turned was roughly equal. The 2010 mid-term elections were also said to have almost equal turnout. This year, the Republicans have been reported to have significantly higher enthusiasm. One might assume that this would mean we could expect a higher Republican turnout. A more conservative approach might assume equal numbers of Democrats or Republicans. However, the published polls tend to be assuming much higher Democratic turnout, with some polls assuming the same Democratic turn out as for the 2008 election.