A much overlooked predictor of Presidential elections is Consumer Confidence in the summer of the election year. This shows how people actually feel about the economy. Sometimes what people feel and what is actually happening is much different.
For instance, in 1992, the economy was growing at a solid 4.2% clip, but because Consumer Confidence was so low, Bush ended up losing reelection.
The lowest level of Consumer Confidence a President has gotten reelected during was 99. Right now, Consumer Confidence is around 60.
Here is Consumer Confidence data going back to 1968 for each Presidential election since:
Year Consumer Confidence level Incumbent party wins?
2008 55 No
2004 103 Yes
2000 139 Won popular vote
1996 105 Yes
1992 62 No
1988 114 Yes
1984 101 Yes
1980 65 No
1976 94 No
1972 99 Yes
1968 131 No
As you can see, a Consumer Confidence reading of 99 or higher is necessary for an incumbent party to hold the White House. Incumbent parties who win have an average Consumer Confidence reading of 104. Incumbent parties who lose have an average reading of 81.
For Obama to be reelected, he needs to raise Consumer Confidence to at least 90 by next summer.