Snake oil doesn't actually cure anything.

It's started.  The Chinese have retaliated for the Trump administration's steel and aluminum tariffs with tariffs of their own on American food products. Pork producers here in Iowa and elsewhere expect to be hit especially hard.

In fairness to the president, the Chinese tariffs are only half as big as his, and the Chinese emphasized that this was simply a matter of economic self-defense and is deliberately limited so as to avoid escalating things. This is not a trade war- yet. But those with the most to lose are nervous. The Dow has tanked. The stock market has had its worst start to the second-quarter since the Great Depression. 

But it does illustrate something history clearly teaches us. Well, most of us; Mr. Trump and his supporters apparently cut class that day. But protectionism is a loser as an economic policy. One does not put tariffs on another country's exports or otherwise impose artificial obstacles to its commerce without inviting retaliation.

The path Mr. Trump and all those Rust-Belt supporters of his who think that protectionism is going to help them keep their jobs seem likely to learn history's lesson the hard way. Protectionism, in the long run, costs American jobs rather than protecting them.

Donald Trump is a demagogue. His trade policy, like so much of his program, is snake oil. Contrary to what some naive commentators seem to think, the more of Mr. Trump's promises he manages to keep the greater a disaster his administration is going to be for the American people and the bigger a laughingstock he is going to be in history.

Trump's only hope of re-election- and it's a very, very slim one- is being prevented from carrying out as much of his problem as possible by cooler heads, whom he can then blame for the fact that his agenda wasn't enacted without being held to account for what would have happened to the country if it had been.