Investors in gold bullion have been suffering brutal losses for more than four years.

The price of gold has nearly halved since its 2011 peak, falling from $1,891 an ounce to just $1,094 today. But last week, for the first time in a long time, there was a bit of good news. Thanks to Donald Trump.

In a remarkable, but little-noticed, exchange during Thursday’s GOP debate, the Republican front-runner opened the door to wider currency wars against America’s main trading partners if he is elected president. And although Trump’s preferred means of retaliating against the likes of China and Japan is apparently through a tariff, similar ends can be achieved far more easily by driving down the value of the U.S. dollar.

And that must surely be positive for gold bullion, the one currency in the world that nobody can print.

“We’ve lost anywhere between 4 and 7 million jobs because of China,” Trump told Fox Business’ Neil Cavuto during the debate. “A lot of that is because they devalue their currency.”

Then he added: “Japan, the same thing.” The Japanese were driving down the value of the yen, he said, and giving domestic manufacturers such as tractor maker Komatsu KMTUY, -0.08% an unfair advantage against U.S. competitors such as Caterpillar CAT, -0.02% . “Friends of mine are ordering Komatsu tractors now because they’ve de-valued the yen to such an extent that you can’t buy a Caterpillar tractor. And we’re letting them get away with it, and we can’t let them get away with it.”

A cheaper yen means anything made in Japan will become cheaper to American consumers, while anything made in the U.S. will become more expensive in Japan.

The essential context for this is that the Japanese yen has slumped since 2012 because the Japanese government has been printing lots more yen to stimulate the economy. It is their version of “quantitative easing,” a policy first launched by the U.S. Federal Reserve back in late 2008.

China is now “easing” its own currency to forestall its sharp domestic slowdown, and currency experts predict they will shortly do a lot more. And they are not alone. The British pound is down to very low levels against the dollar. Ditto the euro, and markets expect further quantitative easing by the European Central Bank in due course.

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Economists have long warned that, in extremis, these policies could lead to a beggar-thy-neighbor scenario, a kind of currency arms race where everyone tries to drive down their currency against everyone else.

Data compiled by the Organisation for Economic Co-Operation and Development, the rich countries’ think tank, show how far this has the potential for mischief. According to the OECD, the yen is now about 10% too cheap against the dollar when measured using “purchasing power parity,” an economic metric that compares prices in both countries. By similar calculations, today’s exchange rates give major trading partners such as Germany and South Korea a price advantage of about 10% against the U.S., and those in other countries and regions, such as Spain, Eastern Europe and Mexico, even cheaper. International Monetary Fund data suggest that China’s currency is already about 20% too cheap when measured by purchasing power parity.

Trump has repeatedly said he is open to tariffs against competitors who compete “unfairly.” The problems with tariffs in practical terms is that they are deeply unfashionable among economists, they are complex to design and implement, and they need to pass both houses of Congress — something that is highly unlikely. Vastly expanding the money supply, through quantitative easing, is much simpler. And simply “talking down the dollar,” by threatening to pursue policies to weaken it, is simplest of all.

And that ought to put a premium on currencies that can’t be expanded — of which gold is the most obvious.

Trump himself has a record of being bullish on gold — ironically for the opposite reason that he believed President Obama was making America “weak.” Indeed, Trump took rent on a New York property in gold bullion right at the peak of the gold market, in September 2011. That proved to be the perfect moment to sell all your shares in gold vehicles such as the SPDR Gold Trust GLD, +0.30%

It’s very tempting to dismiss Trump’s most recent remarks. His campaign for president is consistently buffoonish and outrageous. Yet with voting about to start in the GOP primaries and caucuses, he is the clear front-runner. In the latest RealClearPolitics poll of polls, he leads the field by 15 points, and the man in second place, Sen. Ted Cruz, may face legal issues because he was born in Canada. The bookmakers now make Trump the clear favorite for the nomination at odds of 6/4 — equivalent to about a 40% probability.

The gold market is a mystery wrapped in an enigma wrapped in a conspiracy theory. No one can successfully predict gold prices, and we can’t say for certain that a President Trump would send gold booming back upwards.

But at the very least, if Trump seems set to get the nomination, investors will have to start factoring into their forecasts the possibility of greater economic nationalism and currency wars. If you’re heavily long on the U.S. dollar, or short on gold, that might make you nervous.