Poor Bernie Sanders. How can you expect to become US president if you are not familiar with the relative spheres of competence of the Federal Reserve and Treasury department in the supervision of the nation’s banks? If you are not au fait with the different roles of the Securities and Exchange Commission, the Federal Deposit Insurance Corporation and the Office of the Comptroller of the Currency?

The senator from Vermont was part of the Congress that passed the Dodd-Frank Act extending financial regulation. Yet he has not even mastered the thousand pages or so of the act, far less the regulations and explanatory documents that have been published since.

Mr Sanders’ recent stumbles illustrate a misdirection in his attack on the banking establishment. The central problem is not so much “too big to fail” but “too complex to fail”: Lehman was a systemically important financial institution but not an important financial institution. Nor was it a big one; it had fewer employees than Citigroup today has compliance staff. Lehman’s collapse created major problems for the global financial system because of the extent of its interactions, with more than 1m outstanding contracts at the time of its bankruptcy. Similarly, Long Term Capital Management was insignificant in size when it failed but capable of massive impact by virtue of the exposure of other institutions to its activities.