As a result, the Fed’s attempt to avert a recession has almost certainly failed. And each new piece of economic data  like the news that retail sales fell last month  adds to fears that the recession will be both deep and long.

So now the Fed is following one of the options suggested in that 2004 paper, which was about things to do when conventional monetary policy isn’t getting any traction. Instead of following its usual practice of buying only safe U.S. government debt, the Fed announced this week that it would put $400 billion  almost half its available funds  into other stuff, including bonds backed by, yes, home mortgages. The hope is that this will stabilize markets and end the panic.

Officially, the Fed won’t be buying mortgage-backed securities outright: it’s only accepting them as collateral in return for loans. But it’s definitely taking on some mortgage risk. Is this, to some extent, a bailout for banks? Yes.

Still, that’s not what has me worried. I’m more concerned that despite the extraordinary scale of Mr. Bernanke’s action  to my knowledge, no advanced-country’s central bank has ever exposed itself to this much market risk  the Fed still won’t manage to get a grip on the economy. You see, $400 billion sounds like a lot, but it’s still small compared with the problem.

Indeed, early returns from the credit markets have been disappointing. Indicators of financial stress like the “TED spread” (don’t ask) are a little better than they were before the Fed’s announcement  but not much, and things have by no means returned to normal.

What if this initiative fails? I’m sure that Mr. Bernanke and his colleagues are frantically considering other actions that they can take, but there’s only so much the Fed  whose resources are limited, and whose mandate doesn’t extend to rescuing the whole financial system  can do when faced with what looks increasingly like one of history’s great financial crises.

The next steps will be up to the politicians.

I used to think that the major issues facing the next president would be how to get out of Iraq and what to do about health care. At this point, however, I suspect that the biggest problem for the next administration will be figuring out which parts of the financial system to bail out, how to pay the cleanup bills and how to explain what it’s doing to an angry public.