By PAUL KRUGMAN – New York Times.

A few years back Representative Barney Frank coined an apt phrase for many of his colleagues: weaponized Keynesians, defined as those who believe “that the government does not create jobs when it funds the building of bridges or important research or retrains workers, but when it builds airplanes that are never going to be used in combat, that is of course economic salvation.”

Right now the weaponized Keynesians are out in full force — which makes this a good time to see what’s really going on in debates over economic policy.

What’s bringing out the military big spenders is the approaching deadline for the so-called supercommittee to agree on a plan for deficit reduction. If no agreement is reached, this failure is supposed to trigger cuts in the defense budget.

Faced with this prospect, Republicans — who normally insist that the government can’t create jobs, and who have argued that lower, not higher, federal spending is the key to recovery — have rushed to oppose any cuts in military spending. Why? Because, they say, such cuts would destroy jobs.

Thus Representative Buck McKeon, Republican of California, once attacked the Obama stimulus plan because “more spending is not what California or this country needs.” But two weeks ago, writing in The Wall Street Journal, Mr. McKeon — now the chairman of the House Armed Services Committee — warned that the defense cuts that are scheduled to take place if the supercommittee fails to agree would eliminate jobs and raise the unemployment rate.

Oh, the hypocrisy! But what makes this particular form of hypocrisy so enduring?

First things first: Military spending does create jobs when the economy is depressed. Indeed, much of the evidence that Keynesian economics works comes from tracking the effects of past military buildups. Some liberals dislike this conclusion, but economics isn’t a morality play: spending on things you don’t like is still spending, and more spending would create more jobs.

But why would anyone prefer spending on destruction to spending on construction, prefer building weapons to building bridges?

John Maynard Keynes himself offered a partial answer 75 years ago, when he noted a curious “preference for wholly ‘wasteful’ forms of loan expenditure rather than for partly wasteful forms, which, because they are not wholly wasteful, tend to be judged on strict ‘business’ principles.” Indeed. Spend money on some useful goal, like the promotion of new energy sources, and people start screaming, “Solyndra! Waste!” Spend money on a weapons system we don’t need, and those voices are silent, because nobody expects F-22s to be a good business proposition.

To deal with this preference, Keynes whimsically suggested burying bottles full of cash in disused mines and letting the private sector dig them back up. In the same vein, I recently suggested that a fake threat of alien invasion, requiring vast anti-alien spending, might be just the thing to get the economy moving again.

But there are also darker motives behind weaponized Keynesianism.

For one thing, to admit that public spending on useful projects can create jobs is to admit that such spending can in fact do good, that sometimes government is the solution, not the problem. Fear that voters might reach the same conclusion is, I’d argue, the main reason the right has always seen Keynesian economics as a leftist doctrine, when it’s actually nothing of the sort. However, spending on useless or, even better, destructive projects doesn’t present conservatives with the same problem.

Beyond that, there’s a point made long ago by the Polish economist Michael Kalecki: to admit that the government can create jobs is to reduce the perceived importance of business confidence.

Appeals to confidence have always been a key debating point for opponents of taxes and regulation; Wall Street’s whining about President Obama is part of a long tradition in which wealthy businessmen and their flacks argue that any hint of populism on the part of politicians will upset people like them, and that this is bad for the economy. Once you concede that the government can act directly to create jobs, however, that whining loses much of its persuasive power — so Keynesian economics must be rejected, except in those cases where it’s being used to defend lucrative contracts.

So I welcome the sudden upsurge in weaponized Keynesianism, which is revealing the reality behind our political debates. At a fundamental level, the opponents of any serious job-creation program know perfectly well that such a program would probably work, for the same reason that defense cuts would raise unemployment. But they don’t want voters to know what they know, because that would hurt their larger agenda — keeping regulation and taxes on the wealthy at bay.