Right now there’s intense debate about how aggressive the United States government should be in its attempts to turn the economy around. Many economists, myself included, are calling for a very large fiscal expansion to keep the economy from going into free fall. Others, however, worry about the burden that large budget deficits will place on future generations.

But the deficit worriers have it all wrong. Under current conditions, there’s no trade-off between what’s good in the short run and what’s good for the long run; strong fiscal expansion would actually enhance the economy’s long-run prospects.

A few months ago I found myself at a meeting of economists and finance officials, discussing — what else? — the crisis. There was a lot of soul-searching going on. One senior policy maker asked, “Why didn’t we see this coming?”

There was, of course, only one thing to say in reply, so I said it: “What do you mean ‘we,’ white man?”

Seriously, though, the official had a point. Some people say that the current crisis is unprecedented, but the truth is that there were plenty of precedents, some of them of very recent vintage. Yet these precedents were ignored. And the story of how “we” failed to see this coming has a clear policy implication — namely, that financial market reform should be pressed quickly, that it shouldn’t wait until the crisis is resolved.

Everyone’s talking about a new New Deal, for obvious reasons. In 2008, as in 1932, a long era of Republican political dominance came to an end in the face of an economic and financial crisis that, in voters’ minds, both discredited the G.O.P.’s free-market ideology and undermined its claims of competence. And for those on the progressive side of the political spectrum, these are hopeful times.

There is, however, another and more disturbing parallel between 2008 and 1932 — namely, the emergence of a power vacuum at the height of the crisis. The interregnum of 1932-1933, the long stretch between the election and the actual transfer of power, was disastrous for the U.S. economy, at least in part because the outgoing administration had no credibility, the incoming administration had no authority and the ideological chasm between the two sides was too great to allow concerted action. And the same thing is happening now.

The economic news, in case you haven’t noticed, keeps getting worse. Bad as it is, however, I don’t expect another Great Depression. In fact, we probably won’t see the unemployment rate match its post-Depression peak of 10.7 percent, reached in 1982 (although I wish I was sure about that).

We are already, however, well into the realm of what I call depression economics. By that I mean a state of affairs like that of the 1930s in which the usual tools of economic policy — above all, the Federal Reserve’s ability to pump up the economy by cutting interest rates — have lost all traction. When depression economics prevails, the usual rules of economic policy no longer apply: virtue becomes vice, caution is risky and prudence is folly.