According to a new Zogby poll, Barack Obama’s approval numbers are cratering:

The honeymoon is over, a national poll will signal today as President Obama’s job approval stumbles to about 50 percent over the lack of improvement with the crippled economy. The sobering numbers come as the president backpedals from two prime-time gaffes – one comparing his bowling score to a Special Olympian and another awkwardly laughing about the economy, which prompted Steve Kroft of “60 Minutes” to ask “are you punch-drunk?” Pollster John Zogby said his poll out today will show Americans split on the president’s performance. He said the score factors out to “about 50-50.” Some polls show Obama coasting with a 65 percent job approval, but not in Zogby’s tally. “The numbers are going down,” Zogby told the Herald. “It’s not because of the gaffes, but a combination of high expectations and that things aren’t moving fast enough with the economy.”

Not surprisingly, news of this poll is being touted by many bloggers on the right as evidence that the Obama magic has ended and the public has come to his senses; see, for example, The Other McCain, NO QUARTER, Jules Crittenden, House of Eratosthenes, Whiskey Fire ,and Hot Air.

But there’s something about this poll that just doesn’t make sense.

For one thing, it’s completely out-of-line with every other poll out there. The RealClearPolitics poll average, for example, shows Obama with support levels more than ten points higher than what Zogby reports:

For another, it’s Zogby and his polls have a history of being outliers and unreliable. Back in August, he reported on a McCain surge that never existed based on one of his online interactive polls and, on the eve of the November electionhe released a tracking poll that proved to be completely out of whack with reality.

As it turns out, the poll that was released today is one of Zogby’s Interactive Surveys. In case you’re not aware of these survey’s these aren’t your traditional polls. Instead of calling people at random and filtering for demographics, Zogby lets people sign up for these polls — you can do it yourself here — and then sends emails to the people who have signed up. The results are based on whatever sample of those people actually decides to respond to the solicitation. Because the poll sample is self-selecting rather than random, it violates one of the central rules of reliable polling and, as Nate Silver points out, has a history of being completely unreliable:

[T]hat polling, by the way, has produced some very strange results: in an Internet poll conducted from January 22-26, for example, in the immediate aftermath of Barack Obama’s inauguration, Zogby had Obama’s job approval at 52/29, while the average of polls from five other agencies (Gallup, Hotline, Rasmussen, FOX and Democracy Corps) conducted at the same time put the numbers at avergae of 62/19. Let’s take a look at the track record of Zogby’s Internet polling. Zogby conducted his last series of Internet polls for last year’s Presidential election in mid-October. He missed 3 of 11 states, and was off on the final margin by an average of 5.4 points. (…) All told, between 48 contests that he’s surveyed over the past two election cycles, Zogby’s Internet polls have been off by an average of 7.6 points. This is an extreme outlier with respect to absolutely anyone else in the polling community.

So, despite all the excitement that this poll is bound to generate on the right, it’s fairly clear that it’s pretty meaningless.

Addendum: In the interests of diclosure, I should note that I am on the email list for Zogby’s Interactive Survey and, while I don’t always respond to the solicitation emails they send out every couple of weeks, it’s fairly apparent that I did participate in this poll a couple weeks or so ago because I recognize the question about right track/wrong track.