In his efforts to capitalize on voter discontent, Republican presidential candidate Donald Trump has cranked up his anti-trade rhetoric to appeal to workers who have seen their jobs move overseas.

Among other things, Trump has proposed imposing a steep tariff on products made in China and Mexico.

Unfortunately, there are many more things wrong with tariffs than there are right. To begin with it isn't exactly obvious if imposing tariffs on China and Mexico would bring jobs to the US. Rather, companies seeking these manufacturing cost advantages are like to just move production to one of the many other low-cost countries in the developing world.

Whatever the case, such a protectionist trade policy would cause the cost of production to go up, which means the prices for finished goods would most likely go up for consumers. In other words, no one really wins with tariffs.

"The last American president who was a trade protectionist was Republican Herbert Hoover," wrote Stephen Moore and Larry Kudlow. "Does Trump aspire to be a 21st century Hoover with a moderized plaform of the 1930 Smoot-Hawley tariff that helped send the US and world economy into a decade-long depression and a collapse of the banking system?"

In a note to clients on Friday, Bank of America Merrill Lynch's Michael Hartnett considered economic and financial market scenarios under the regimes of the presidential candidates. Like Moore and Kudlow, Hartnett reflected on the Smoot-Hawley act.

“An extreme example [of trade protectionism] admittedly, but the 1930 Smoot-Hawley Tariff Act that increased US import duties by as much as 50% was extremely bearish for risk,” Harnett observed. “In a world today devoid of corporate confidence trade tariffs, capital controls, border controls are unlikely to engender risk-seeking behavior on Wall Street, though Main Street may temporarily benefit.”

It would be an understatement to say there were a lot of other things going on in the late 1920s and early 1930s that contributed to the downturn in the markets and economy. But almost everyone agrees that the tariffs only made things worse.

Hartnett note that trade protectionism is bearish for stocks (^GSPC), while bullish for gold (GLD).

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Sam Ro is managing editor at Yahoo Finance.

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