The problem is that the alternative to a Fed response is, at the moment, not obvious. The Biden administration’s attempts at tamping down price increases — longer port hours, release of strategic petroleum reserves, calling out corporate price gouging — have mostly tinkered around the edges of the issue.

Those kinds of precise moves to counter inflation are what M.M.T. economists would recommend, though. Ms. Kelton laid out other suggestions M.M.T. economists have made in a recent blog post. Among them: Medicare for All, cutting the Pentagon budget, repealing some tariffs and unclogging the ports.

Not exactly “easy peasy,” to borrow a phrase of hers.

“M.M.T. was already pretty marginal,” said Jason Furman, a Harvard economist, noting that, in his view, most policymakers and prominent academics ignored it already. Even if policy in the pandemic effectively embraced the idea that you do not have to pay for your spending, that idea, he said, was also Keynesian.

And the M.M.T crowd, while dismissing the Fed’s role, has not come up with a clear and obviously workable idea for how to stem inflation, he argued, adding, “If you were open-minded, this would discredit it still further.”

In Washington, the suite of ideas has clearly been dealt a setback. Deficit concerns have returned. Mr. Biden’s sweeping policy agenda has not passed because Senator Joseph Manchin, a West Virginia Democrat and member of his own party, has opposed it on concerns about government debt and inflation.

Despite that, some of M.M.T.’s proponents are still sounding celebratory.

“We’ve won the debate on the intellectual level — there are no flaws,” Mr. Wray said.

Flaws or not, there are questions.

Questions like: “Did Congress ‘experiment’ with MMT, and does the run-up in inflation mean that MMT has ‘failed’?”