Of all the e-mails unearthed from that weekend, however, a two-sentence note from Mr. Bernanke to a colleague on the Sunday night while Lehman was in the process of filing for bankruptcy speaks volumes: “In case I am asked: How much capital injection would have been needed to keep LEH [Lehman] alive as a going concern? I gather $12B or so from the private guys together with Fed liquidity support was not enough.”

In other words, the chairman of the Federal Reserve didn’t even know how much money would have been required to rescue Lehman, even temporarily. (In fairness, he has argued that the ultimate amount of money needed was almost irrelevant because the Fed would have been lending into a “run on the bank.”)

Of course, the disclosed e-mails were cherry-picked by the Financial Crisis Inquiry Commission and surely do not provide a complete picture of the discussions in those last 72 hours.

But what is clear is that the politics of the moment played a factor  or at least was discussed among senior and junior staff  in the decision not to lend to Lehman Brothers, perhaps the greatest mistake of the crisis.

While there is no question that our leaders at the time worked around the clock to find a private market solution for Lehman  and I have praised them in this column for staving off another depression in the wake of the panic that followed Lehman’s collapse  its failure should go down in history as a gigantic misstep. (In truth, though, no one has yet to offer up another option for the government.)

In defending its decisions, Thomas C. Baxter Jr., the general counsel of the Federal Reserve Bank of New York, said at the hearings last week, “The Federal Reserve did not ‘allow’ Lehman Brothers to die.”

In an interview, Mr. Paulson acknowledged that many of his colleagues pressed him to make decisions based on politics, but said that “I never once let politics or public sentiment interfere.” He added: “If we could have found a legal means to save them we would have.”