Its actually quite unusual for the stock market to react negatively the day after an election - usually there is some sort of "post-election rally"
regardless of who wins because the election of a new president resolves uncertainty, and markets dislike uncertainty. The market has gone up on days
before with worse economic data, so this is seems to be a clear message that investors are concerned about the next 4 years.
www.bloomberg.com
(visit the link for the full news article)

