In fact, that poll, conducted by The Economist/YouGov, was Mr. Obama's strongest performance, save one poll. The others, conducted by Reuters, Fox News, and Rasmussen, showed the President at, respectively, -7, -8, and -8.
And then you have Gallup, which has the President at +7. That's 13 points away from the closest poll since June the 24th. In fact, on June 23, Gallup had the President down four percent, with an approval rate of 45% and a disapproval rate of 49%. That's an 11 point swing.
In trying to piece together how the Gallup could get such vastly different numbers, I looked at who they polled. First, their questionnaire was anonymous. Rasmussen polled likely voters, while Fox and YouGov polled registered voters. However, Reuters polled anonymously as well, so that alone as a factor is out.
Third, I tried to look at who exactly each pollster asked, and found at least some reason for the discrepancy. Other than Gallup, each news organization included very specific numbers on who they polled and what they found. These include demographics, party alignment, age, gender, and so on.
Literally all the information that Gallup provided, other than the poll numbers they found and previous poll numbers, was this short statement:
Gallup tracks daily the percentage of Americans who approve or disapprove of the job Barack Obama is doing as president. Daily results are based on telephone interviews with approximately 1,500 national adults; Margin of error is ±3 percentage points.That's it. Nothing more, nothing less. The fact that they, essentially, are hiding who they're asking questions too speaks to how they are so opposed to every single other poll out there.