Nate Silver, FivethirtyEight
The old Bill Clinton campaign slogan now has some evidence behind it thanks to Nate Silver. Note how strong the correlation between Economic Approval and Overall approval is. Now, both could be moving together for reasons that have nothing to do with the underlying strength economy - like an advertising blitz on America's recovery during the 2012 Presidential campaign. It does happens. But that is not what is happening right now. Housing is picking up. The stock-market is at an all-time high. Layoffs have been trending downwards. Unemployment is down. The economy is recovering and Obama is given credit for it, whether he deserves it or not.
For those who have not read it, I highly recommend Nate Silver's book.