Expect stocks to tumble if Donald Trump has a great first debate night.Wall Street doesn’t want a President Trump (with the exception of a few hedge fund managers and Trump supporters, like Carl Icahn). As the old saying goes, the market loves good news, it can deal with bad news, but it hates uncertainty. And Trump is the motherlode of uncertainty.“The typical investor just can’t contemplate the possibility of a Trump victory,” says Cary Leahey, chief U.S. economist at Decision Economics.As polls tighten — CNN now calls it a “dead heat” — Wall Street is having to come to terms that the possibility of a President Trump is real…and rising. With the debate looming on Monday, the Dow fell 167 points.A strong debate performance by Trump on Monday will exacerbate those worries.“If for some reason Trump puts on a presidential showing…and Clinton stumbles for whatever reason, then the market may take another reassessment,” says Leahey. That’s the polite way of saying, stocks are likely to fall.I noted this in the debate: “Believe me, we are in a bubble right now, and the only thing that looks good is the stock market, but if you raise interest rates even a little bit, that’s going to come crashing down. We are in a big, fat, ugly bubble,” the Republican presidential nominee said Monday night.This statement makes sense considering Trump’s people are the kind of people who found Zerohedge a few years ago and are sure that its latest prediction of imminent market collapse is for real this time. Any day now.A likely Donald Trump post campaign activity will be to start selling his own gold coins to protect against the imminent global financial apocalypse. Considering his track record with his late-to-the-party, me-too entry into mortgages, premium vodka, real-estate seminars, and Sharper Image partnerships, a Trump entry into gold hawking is a huge sell signal on gold.Actually, you should probably sell your gold as it is. I wouldn’t expect anything more than flat for the next 15 years.