I made this call on my facebook page on election day, but figured I'd elaborate on it here. Obama will get credit for both the inevitable economic recovery and the end of the Iraq war (both of which would have happened regardless of who is President), which should likely guarantee a second term.
It is annoying that president's get credit for just standard movements along a business cycle that are out of their control. Reagan won re-election because of it, Carter lost for largely the same reason.
More broadly, Obama like Clinton will benefit from a large peace dividend. Clinton likes to claim credit for balancing the federal budget, but more credit should go to an intransigent Newt Gingrich led Congress, balanced budget laws passed under his predecessor, and military spending (as % or GDP) that had halved in the past 10 years.