“After simmering early in the year, trade policy tensions nearly boiled over in May and June, but now appear to have returned to a simmer,” as Mr. Powell summarized in his news conference Wednesday. President Trump turned the metaphorical stove back to high less than 24 hours after those words passed Mr. Powell’s lips.

This suggests the president and his trade negotiators believe they have downside protection against the possibility that trade policies will cause any lasting damage to the economy or the stock market. After all, the Fed has very publicly shown that it views it as appropriate to cut interest rates to combat any slowdown related to trade wars.

There is always interplay between different elements of economic policy set by various parts of government. For example, the Fed’s practice is to take tax and spending decisions by Congress as a given and plug them into its models — and adjust its interest rate policies accordingly.

What’s different now is that Mr. Trump’s administration seems willing to weaponize that practice, offering no qualms about openly bullying the Fed while using its presumed reaction as a source of advantage in international negotiations.

Even as Mr. Trump is comfortable abandoning the norm that the president should not explicitly pressure the Fed, Mr. Powell appears to be obeying the tradition that the Fed should not try to use its power over monetary policy to twist the arms of elected officials.

It has worked out fine for Mr. Trump so far — the economy continues to grow heading into an election year, and while the stock market fell Wednesday after the latest trade news, the S&P 500 was down only 0.9 percent; it would surely have been down more if not for assumptions that further rate cuts were now more likely.

But it also creates a number of risks for the American economy, in both the short and longer term.

First, the Fed’s interest rate policies are blunt instruments. They seem to be more effective at generating big swings in asset prices than at fine-tuning the economy, and it would be easy for Mr. Powell and his colleagues to make a mistake — either cutting interest rates by too much, fueling inflation, or too little, allowing a slump.