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.

Here’s Ohio:

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.

If it comes down to whether or not this will be a repeat of 2008 -- which is basically what the latter camp of pollsters is suggesting -- then my money is on no. Of course, it is possible that I am wrong. I have no crystal ball looking forward. All I can do is look back through history, where I see on average a nationwide Democratic identification edge of about 3 points, which is also roughly the midpoint between 2004 and 2008. That is my guess about 2012. It is an informed guess, but it is still a guess. If I’m right, then Rasmussen, Purple Poll, Mason-Dixon, and Survey USA are closer to the mark. But I could be wrong, in which case Fox, PPP andWashington Post are closer to the mark.

Importantly, the pollsters are guessing, too. They are guessing via the myriad of choices they make about when to poll, whom to poll, and how to poll. By Election Day, polling will be much more “scientific” than it is today; but now there is quite a bit of “art.” That's how we wind up with two points of convergence, instead of just one.

Another point to keep in mind: bimodal distributions are extremely messy to deal with. It is hard to average them in a meaningful way, and analysts who build complicated predictive models based on these sorts of polls are going to have a difficult time handling them.

Second major point: There is a subtler dimension to this Democratic polling advantage, one that nevertheless exercises a powerful effect on the margins between the two candidates. And it looks to apply to most of the polls, at least for the time being. It has to do with how tightly the two sides have control over their own coalitions. For instance, a recent Rasmussen poll had Romney winning 85 percent of Republicans, and Obama winning 11 percent. So, we might say that Romney is pulling a net of 74 percent from his own side.

We can replicate this methodology for recent polls that provide enough data.

As we can see, Obama has tighter control over his base at the moment. Now, the difference may seem insubstantial, but I assure you it is not. After all, this is a race that will see the two sides separated at most by 5 points, so this basically gives the president a one-point boost over Romney, simply by virtue of having a more unified base.

But is this historically accurate? Not really. In fact, over the last forty years, Republican candidates have consistently had tighter control over their base than their Democratic counterparts. Here is the most recent historical data from the exit polls:

The GOP control over its base has been remarkably consistent over the last forty years (at least in years without a major third party challenger), falling within a very tight range of +81 and +87, for an average of +84 over the last three cycles. The Democrats, meanwhile, had problems up through the 1980s, as the old New Deal/Great Society coalition was breaking down. Nevertheless, the party has since been rebuilt with a relatively loyal base of support. If we control for the Nader factor in 2000 breaking apart the Democratic base at the margins, then they are probably averaging about 78 or 79 percent these days.

Notice that the GOP outpaces the Democrats in party unity. That was true even in 2008, which was the best year for the Democrats and the worst for the Republicans in a generation. But notice also that the average of recent polls has the Democrats more unified than the GOP. That is a historical anomaly.

Again, it is possible that history will be defied, but I am rarely one to bet on that happening. If we instead assume that the GOP will have a net of +84 among its own partisans, and Obama can recreate the +79 he managed in 2008, then we are talking about a 2-point shift in these polls in favor of Romney. In other words, the above national polls give Obama a 3.6 percent edge over Romney; if the two bases fall back into historical alignment, then that lead would be cut to about 1.5 points.

As with the first point, I’m not saying that any of this will happen. But I suspect that when the Democratic enthusiasm bump from the DNC finally settles, we are going to see the two parties sort themselves roughly in line with what they have done through history – meaning a slight edge for the Republicans, not the Democrats. That is also going to shrink Obama’s margin.

Final thought: As I mentioned earlier, a big “tell” here is that Obama cannot build any kind of lead among independent voters. That suggests to me that his advantage is built entirely on Democratic enthusiasm, which right now is above its historical trends and clearly on a post-DNC bump. Nobody in the postwar era has won the presidency by carrying less than 49 percent of independents, and Obama is quite a ways below that mark, even if some polls show him at or above 50 percent nationwide and in the key swing states.

Jay Cost is a staff writer for THE WEEKLY STANDARD and the author of Spoiled Rotten: How the Politics of Patronage Corrupted the Once Noble Democratic Party and Now Threatens the American Republic, available now wherever books are sold.

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