Again, they insisted that austerity was essential because government debt was an enormous threat to America. But they lost all interest in deficits as soon as one of their own occupied the White House. Trump inherited a $600 billion deficit; he’s blown that up to $1 trillion — and hardly a single Republican in Congress has expressed dismay.

How much have Trump’s deficits boosted the economy? Well, they’re poorly designed stimulus; the biggest item was tax cuts for corporations, which corporations used to buy back stock rather than to expand their businesses or raise wages. But while the Trump stimulus probably didn’t deliver much bang per buck, it involved a heck of a lot of bucks.

And Trump’s economy also gets a lift from the fact that Republicans have ended the de facto economic sabotage that prevailed throughout the Obama years.

Incidentally, the experience of the past three years also refutes two of the main arguments used to justify the disastrous turn to austerity after the financial crisis — claims that deficits would hurt confidence and lead to a sharp rise in interest rates. None of this has happened.

So how can Democrats run against Republican fiscal hypocrisy? Not by warning about the dangers of deficits — that’s both wrong on the substance and politically ineffective, because nobody cares.

They might do better by pointing out that while Trump has rushed to cut taxes for corporations and the wealthy, he has been shortchanging the future. Ignoring his campaign promises, he has done nothing to raise much-needed spending on infrastructure. And despite its obvious indifference to budget deficits, his administration seems determined to deprive children of the adequate health care and nutrition they will need to become productive adults.

And there’s an important lesson for Democrats going beyond this election — namely, how to deal with what I’ve called the Very Serious People, centrists who spent years insisting that government debt was the most important issue of our time (and also believing, or pretending to believe, that Republicans were sincere in their supposed concern about debt).

The V.S.P.s have gone oddly silent under Trump — funny how that works — but they’ll surely be back if Democrats retake the White House. But they have no idea what they’re talking about, and never did. If and when they re-emerge, Democrats should ignore them.

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