Wall Street's long-running view that Hillary Clinton would easily become the next president has been replaced by a new fear that Donald Trump could win, and it probably won't be a pretty picture for stocks if he does.

Bond yields have moved lower and so have stocks, as the markets have begun to react to the possibility of a Trump victory in the last several days. On Thursday, the S&P 500 was up slightly, after falling 13 points Wednesday, to close at the key support level of 2,097.