Among the many polls released every day, one always stands out. The Gallup Poll is arguably the most trusted survey brand in the world, a name virtually synonymouswith public opinion polling. It has measured presidential job approval and vote preference without interruption since the 1940s and now conducts a daily tracking poll that reaches more than 3,600 adults every week -- a volume of data that dwarfs that produced by other firms. As a result, Gallup's numbers enjoy unique influence and public prominence.

Over the past few years, however, polling junkies have noticed something curious: Gallup's polls have produced results that appear slightly but consistently more negative to President Obama than those produced by other firms.

The Huffington Post has conducted an independent analysis that confirms the phenomenon and points to a likely explanation. The problem lies in the way that Gallup handles the racial composition of its samples, and the findings highlight significant issues with how polls are developed and conducted today.