Jonathan Freedland wrote an article for the Guardian that makes a lot of sense to me.

Because Fox has put off the best Republican candidates, Barack Obama will be much less vulnerable at the election

Whoever wrote the political rulebook needs to start rewriting it. It used to be an iron maxim that voters' most vital organ was neither their head nor their heart, but their wallet. If they were suffering economically, they'd throw the incumbents out. Yet in Britain a coalition presiding over barely-there growth, rising unemployment and forecasts of gloom stretching to the horizon is holding steady in the opinion polls, while in the US Barack Obama is mired in horrible numbers – except for the ones showing him beating all-comers in the election now less than 11 months away. Even though the US economy is slumped in the doldrums, some of the country's shrewdest commentators make a serious case that Obama could be heading for a landslide victory in 2012. How to explain such a turnaround? In the United States, at least, there is one compellingly simple, two-word answer: Fox News. I think he's 100% correct. Worth the read.