If the anti-free trade rhetoric by Republican front-runner Donald Trump on the "extreme right" and Democratic candidate Sen. Bernie Sanders on the "extreme left" were to become U.S. policy, the economy would suffer greatly, said Richard Fisher, who retired as Dallas Fed president last year and served as deputy U.S. trade representative during the presidency of Bill Clinton.
"Protectionism is the crack cocaine of economics. We know that it gives you a high. But it can be super-deadly, economically speaking," Fisher told CNBC's "Squawk Box" on Monday.
Currently a senior advisor to British banking giant Barclays, Fisher said there's a long history showing that taxing foreign goods in an attempt to affect a level playing field on trade does not work. "We know about Smoot-Hawley, which was a tariff imposed deep in the Great Depression and actually drove the world into depression."
Sponsored by Utah Sen. Reed Smoot and Oregon Rep. Willis Hawley, the Tariff Act of 1930 raised U.S. tariffs to historically high levels.
Fisher said the case against isolationist trade policy goes back even further. "Benjamin Harrison ran for the presidency [in 1888] on a protectionist, high tariff, same kind of rhetoric you hear today. He won. And we went into one of the great depressions of all time ... which lasted longer than the Great Depression that we talk about."