Are the presidential polls skewed?

[nomoon]

TJkelli,

Thank you for your contribution. I appreciate your polite input.

I don’t think that it really matters whether they explicitly weighted by party at the outset, or they merely used another method to determine party turnout. The reported polling results still reflect assumed party turnout. Are the assumed turnout values reasonable? I think that a reasonable and a valid consistency check is to look at the polls’ assumed party turnout and compare it to other metrics and benchmarks. If the turnout numbers don’t look reasonable, then maybe there is a problem with the model that was used to determine turnout.

I’d say that before the debates, the poll predictions were more uncertain for a number of reasons. Right leaning votes tended to have more ambiguous feelings about Romney. The Guardian article was published on Sept 17, 2012, so the graph data was from polling before the debates. The data from my graphs were from last week, which was after the debates. The more recent polls (like the post-debate graphs I posted) appear to have a more robust trend, and aren’t dependent on a single data point. If I have time, I’ll try to generate an undated graph.


A premise to the view that the polls are not skewed (I’m using the word “skew” to include indirect skewing based on turn out models), is that Republican party affiliation is not popular, and that fewer people are self identifying themselves as Republicans. The remaining self-identified Republicans are still reliably voting Republican at a roughly 90% rate like Democrats are reliably voting Democrat at roughly 90%. The pool of independent voters now includes a population of people who previously self-identified as Republican, so it’s not surprising that the independents are leaning towards Romney. The Romney-leaning independents cancel out the shortfall of self-identified Republican voters, so the net totals reveal a closely matched race.

HOWEVER:
If I recall correctly, the current party turnouts for the Obama-leaning polls have turnout numbers that roughly match the turnout for the 2008 election. If party affiliation hasn’t changed since then, then this would be plausible. However, if I recall correctly, the 2010 elections had roughly equal numbers for Republican and Democrat turnout. If so, then the premise that the Republican Party has lost popularity and that the number of self-described Republicans has significantly dropped may be invalid. By “significantly” dropped, many of the polls show a drop from ~37% to ~30%, which would mean a drop of ~19% of party membership. That seems like a lot. Also, I understand that there is currently a mismatch of party enthusiasm, where the Republicans have higher enthusiasm, which would be expected to raise the relative turnout of Republicans.

You make a good point about the pollsters having an incentive to be accurate. However, I don’t think that the polling community is any more immune to political biases than the study of economics. According to the Limbaugh hypothesis, the polling firms may drop their skewing at the last minute so that their final polls better reflects reality and they can claim that their polls were accurate the whole time. I’m not sure that I’m that cynical, but I’ll be watching. Wasn't there a Gallop article last week which explicitly measured expected voter turnout by party, they reported a Republican turnout that matched Democrat turnout? (Sorry, I can't find the link now).

One nice thing about this issue is that we’ll hopefully know by Tuesday.