If Donald Trump becomes the next president, stocks will fall 50 percent, according to Wedbush's director of equity sales trading.

That's based on his analysis of the effects Trump's economic policies would have if the GOP front-runner carried them out as president.

In making his bold call, Ian Winer first looks at Trump's proposal to cut taxes on the highest-earnings Americans and on corporations, which according to different sources, would reduce government revenue by something in the neighborhood of $10 trillion over the next decade. On the spending side, Trump has promised to bulk up the military and bolster the country's infrastructure, which could lead to increased rather than reduced expenditures.

"Without any cut in spending, it's probably going to require somewhere between 8 and 9 percent GDP growth just to make us neutral," Winer said Tuesday on CNBC's "Fast Money."

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In other words, a massive increase in the country's deficit is likely, which could reduce the country's credit position.

The second policy plan Winer analyzes is one of Trump's best known — his promised mass deportation of undocumented immigrants. Not only will this cost a great deal of money to carry out, but it would massively deplete America's labor supply, Winer said.

"If you assume that every one of the 11 million people leave, and for every one of those jobs an American takes it — which probably is not likely, but let's just say they do — they're going to be higher-wage jobs," Winer said. That would "cut into corporate margins, and at the end of the day, it's just going to result in higher prices for consumers when they go to Wal-Mart and when the go to buy things."

Finally, Winer takes a look at the tariffs proposed by Trump on imports from China, Mexico and elsewhere.

"All this would do would be to raise prices on the poor," as it would directly increase the prices of goods, Winer wrote. "All it really does is impose a tax on U.S. consumers."

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All in all, Winer believes Trump's policies would lead to a nation on weaker fiscal footing, with a lack of cheap labor and a lack of cheap goods. In this environment, the multiple paid on S&P 500 earnings would dramatically decrease, he said.

"If all the policies are enacted," the S&P's price-to-earnings ratio "could go as low as 11," which is how you "get to 1,000 on the S&P," Winer wrote.

That would represent a 50 percent drop from current levels.

Winer isn't alone in predicting that a Trump win will hurt stocks. Byron Wien of Blackstone and Joseph Grano of Centurion Holdings made similar points in recent interviews on "Fast Money," though neither went so far as to say it could lead to a 50 percent crash.

For the other side, click here to see Trump's arguments.