Political scientist John Sides has created a model that predicts presidential approval ratings based on various factors, including economic conditions and approval ratings of past presidents.
As the chart above indicates, Barack Obama has defied the model’s expectations.
Sides attributes this phenomenon to Obama’s likability and to the fact that most Americans still blame George W. Bush for the economy.
Ezra Klein offers a THIRD REASON:
[T]he Republican Party isn’t offering a very compelling alternative right now, and so Obama’s numbers are, in part, a relative judgment given the options available to voters. It’s easier to say someone is doing a bad job when there’s someone you can point to who looks like they’re doing, or at least could do, a better one.