The formal debates among the Republicans who would be president have exceeded all expectations. Even the most hardened cynics couldn’t have imagined that the candidates would sink so low, and stay so focused on personal insults. Yet last week, offstage, there was in effect a real debate about economic policy between Donald Trump and Mitt Romney, who is trying to block his nomination.

Unfortunately, both men are talking nonsense. Are you surprised?

The starting point for this debate is Mr. Trump’s deviation from free-market orthodoxy on international trade. Attacks on immigrants are still the central theme of the Republican front-runner’s campaign, but he has opened a second front on trade deficits, which he asserts are being caused by the currency manipulation of other countries, especially China. This manipulation, he says, is “robbing Americans of billions of dollars of capital and millions of jobs.”

His solution is “countervailing duties” — basically tariffs — similar to those we routinely impose when foreign countries are found to be subsidizing exports in violation of trade agreements.

Mr. Romney claims to be aghast. In his stop-Trump speech last week he warned that if The Donald became president America would “sink into prolonged recession.” Why? The only specific reason he gave was that those duties would “instigate a trade war and that would raise prices for consumers, kill our export jobs and lead entrepreneurs and businesses of all stripes to flee America.”