America’s use of torture has betrayed not just American values but our national security, right to the present day.

In her telling, a major incentive for Mr. Cheney’s descent into the dark side was to cover up for the Bush White House’s failure to heed the Qaeda threat in 2001. Jack Cloonan, a special agent for the F.B.I.’s Osama bin Laden unit until 2002, told Ms. Mayer that Sept. 11 was “all preventable.” By March 2000, according to the C.I.A.’s inspector general, “50 or 60 individuals” in the agency knew that two Al Qaeda suspects — soon to be hijackers — were in America. But there was no urgency at the top. Thomas Pickard, the acting F.B.I. director that summer, told Ms. Mayer that when he expressed his fears about the Qaeda threat to Mr. Ashcroft, the attorney general snapped, “I don’t want to hear about that anymore!”

That’s why the Bush White House’s corruption in the end surpasses Nixon’s. We can no longer take cold comfort in the Watergate maxim that the cover-up was worse than the crime. This time the crime is worse than the cover-up, and the punishment could rain down on us all.