The stock market historically have dropped after the initial midterm election and bounced back up later.
A CNBC analysis found that after the three midterms (1986, 1990 and 2006) when Democrats controlled both houses and a Republican held the presidency, the S&P 500 averaged a 0.5% decline on the reaction day but was up 3.4% a month later and 10.9% after a year. - CNBC.