Leave aside what the now-famous video tells us about Mitt Romney’s character; in a way the shocking thing is how uninformed he seems to be. The 47 percent number was the kind of thing you hear in yahoo forums like talk radio and the Wall Street Journal editorial page; and then there’s what he said about US debt.

Kevin Drum makes the catch:

[A]s soon as the Fed stops buying all the debt that we’re issuing—which they’ve been doing, the Fed’s buying like three-quarters of the debt that America issues. He said, once that’s over, he said we’re going to have a failed Treasury auction, interest rates are going to have to go up. We’re living in this borrowed fantasy world, where the government keeps on borrowing money.

Has the Fed been buying anything like three-quarters of the debt that we’re issuing? Here’s a comparison between two numbers: the increase in the value of federal debt held by the public (which in this case includes the Fed), and the increase in Fed holdings of federal debt, in each case measured over the previous year:

So there was a period when the Fed was buying a large fraction of federal debt issue — but it didn’t last long. Many people did believe that terrible things would happen when the Fed stopped — among them Bill Gross. And you know what? They lost a lot of money, because the Fed bond purchases came to an end but interest rates kept going down:

And yes, I called this one right. But that’s not crucial here. What is crucial is that a sort of urban legend developed that the only thing keeping rates low was the Fed; this legend was proved wrong by events; but Mitt Romney still believes it.

And why does he believe it? Because he talked to some guy.

Look, Romney is a presidential candidate. He has a staff, and some prominent economists allegedly advising him. Yet he draws his stories about the economy from what he heard somewhere, apparently believing that if the right sort of person says something there’s no need to check it out.

Awesome.