It comes by way of Goldman Sachs, which Adam flagged below, but is worth reproducing in part:
The US growth outlook has brightened significantly in recent weeks. As a result, we have raised our sights for 2011, calling for real GDP growth to average 2.7% for the year versus 2.0% previously. We expect growth to pick up further in 2012—to 3.6% on average for the year—though judgments that far out are clearly tentative.
It is likely that nothing President Obama or any of his Republican foes say or do over the next two years will matter as much as these numbers, which are sure to change again with time.
For comparison: GDP growth for Richard Nixon in the second half of his first term was 3.4% and 5.3%. (He won reelection.) Jimmy Carter had 3.1% and -.27%. (He lost.) Ronald Reagan had 4.5% and 7.2%. (He won.) George H. W. Bush had -.23% and 3.4%. (He lost.) Bill Clinton had 2.5% and 3.7%. (He won.) George W. Bush had 2.5% and 3.6%. (He won.)
If these projections hold, which is a big if, Barack Obama will enter the polls in 2012 with GDP growth of 2.7% and 3.6%, which looks a lot like what Bill Clinton and George W. Bush enjoyed. This is by no means outstanding. But neither is it prohibitive, like it was in the 2010 cycle. GDP growth over the last two years has been -2.6% and 2.4%, which evens out to a big fat goose egg. But you already knew that.
To look at the growth rates yourself, see this handy spreadsheet.