According to a recent study by the Hirsch Organization, publishers of the Stock Trader's Almanac, if the Dow loses more than 0.5 percent of its value in the month of October before Election Day, then an incumbent president is going to lose his job. The Dow fell 0.52 percent in October.

This predictor has been true without exception from 1904 to the present, according to Jeffrey Hirsch, editor of the Stock Trader's Almanac and president of the Hirsch Organization.

http://money.cnn.com/2004/10/29/markets/election_dow/index.htm