An election without a clear winner the following day would likely weigh on the benchmark S&P 500, which is up nearly 45% since its March lows and hovering near record highs. The S&P 500 fell 1.8% the morning after the disputed Nov. 7, 2000 election between Democrat Al Gore and Republican George W. Bush, and fell 5% by the end of the week, according to data from Capital Economics.