Morning Jay: Are the Polls Tilted Toward Obama?
6:00 AM, Sep 26, 2012 • By JAY COST
Republicans, by and large, are frustrated with recent polls of the presidential election because they think Democrats are being oversampled. Many pollsters respond by saying that “weighting” the polls for partisan identification creates its own problems and might end up skewing the polls in the wrong direction.
I am not in favor of partisan weighting, per se, although some polls like the Rasmussen poll do it in a sensible and nuanced way. So, I think the pollsters are offering a false choice between weighting and not weighting.
Furthermore, a lack of weighting creates its own problems, which many pollsters often fail to acknowledge. Specifically, many polls have, in my judgment, overestimated the Democrats' standing right now. I base this conclusion not on a secret, black box statistical methodology or some crystal ball, but rather on a read of American electoral history going back to 1972. If I am right, then some of the polls are giving a false sense of the true state of the race, and will likely correct themselves at some point or another.
One important “tell” in my opinion, is this president’s continued weak position with independent voters, who remain the true swing vote.
Obama’s average overall margin over Romney in these same polls is roughly 4 percent. Bottom line: You do not get a four-point lead overall with a tie among independents, unless you are squeezing substantially more votes out of your base than your opponent is. And more generally, you are not "winning" an election in any meaningful sense of the word when 3/5ths of unaffiliated voters are either undecided or against you.
So, I see two ways the polls are tilted in favor of the president.
First, many of the polls are guessing that Democrats are set to turn out at levels that match or sometimes exceed 2008. Take two examples – recent polls in Ohio and Florida. I’ve included the 2008 and 2004 exit polls as a baseline for consideration.
The midpoint between 2004 and 2008 is D+1.5. You’ll notice that Gravis, Washington Post, and Fox basically see a replay of 2008 while Rasmussen and the Purple Poll see roughly something in between 2004 and 2008. Relatedly, the polls on the high end for Democrats see a 5-point lead or better for the president (with Gravis being a strange exception), and Obama at or near 50 percent. The polls that see a tighter partisan split basically see a toss-up.
We see the same thing in Florida as well.
The median between 2004 and 2008 is actually a Republican advantage of 1.5 points. But, once again, only Rasmussen and the Purple poll show anything like that. The rest of them tilt toward 2008, with several of them overwhelmingly so. And, once again, the polls that feature “2008 Mach 2.0” show a very healthy Obama lead; the polls that see something between 2004 and 2008 show a pure toss-up.
We also see the same tendency in Virginia, Colorado, and, as best I can tell, Nevada (there has been less polling there).
All told, we see a statistically significant relationship between Obama's margin and the Democratic advantage in partisan identification. In other words, there appears to be a bimodal distribution of the polls. They are not converging around a single point. Instead, some (notably Rasmussen, Purple Strategies, Survey USA, and Mason-Dixon) see Obama ahead by just 1 to 3 points in the key swing states, while others (notably the Washington Post, Fox News, PPP, and NBC News/Marist) see an Obama lead that ranges between 4 and 8 points. And the difference looks to be built around how many Democrats are included in the polling samples.