From the WSJ:
While the 7.7% rate in November 2012 would be the highest in seven presidential election cycles, analysts point out that it is often the overall trend—rather than the level of joblessness—that determines an incumbent's fate. President Carter was defeated in 1980 by Ronald Reagan when the unemployment rate was 7.5%, lower than the level when he was elected but up from 5.6% earlier in his term. Meanwhile, President Reagan was re-elected in 1984 with the rate at 7.2%, but that was down sharply from the peak of 10.8% recorded in 1982.
The early 1980s recovery moved at a much faster pace than the current upturn, especially in the job market. The 1984 election was held two years after unemployment hit its cyclical peak, and had already fallen by 3.6 percentage points. By contrast, the most recent peak in the jobless rate was at 10.1% in October 2009, and if economists are correct, that would mean a decline of just 2.4 percentage points in more than three years.
While none of the current economic projections suggest that the level of growth over the next year will be similar to the rate of growth enjoyed by Reagan in the run-up to his his 1984 reelection, political handicapper Charlie Cook argued recently that it likely won't have to.
Cook said that "a decline to around 8 percent would likely bode well for Obama's reelection chances. If it remains around 9 percent, one can argue that most any major Republican nominee has a good chance of winning."