What would the American presidency be without secret tapes? There were the Watergate tapes that destroyed Richard Nixon. There were the copious Oval Office recordings of John Kennedy and Lyndon Johnson, less explosive, but hugely revelatory nonetheless. And now, almost inevitably and potentially the most revealing of all, there are the Clinton Tapes – or rather two sets of tapes.
One boxful, whose transcripts fill a shelf of the Clinton home in Chappaqua, New York, cover the 79 conversations the former president held with his old friend Taylor Branch, esteemed biographer of Martin Luther King and co-worker with Bill and Hillary on George McGovern's ill-fated White House campaign of 1972.
The conversations took place over virtually the entire span of the Clinton presidency, between September 1993 and January 2001. For each of them, Mr Taylor was summoned down to Washington from his home in Baltimore, usually in the late afternoon.
Sometimes the 42nd president would be exhausted. "The only time he could fit me in was when he was tired," Mr Branch told GQ magazine this month. "There were stunning moments. I would be talking to him late at night, and his eyes would roll back in his head. He would fall asleep in the middle of a sentence."
But the recordings themselves remained in the White House, hidden by Mr Clinton in a sock drawer for fear their existence might become known. Had that happened, the tapes would surely have been subpoenaed as evidence in one or other of the scandals dogging his presidency.
So, when each talk was over, Mr Branch would make the hour-long drive back to Baltimore, along the way dictating tapes of his recollections of what his friend of 20-plus years had just said. These now form the basis of a 700-page book, The Clinton Tapes: Wrestling History with the President, about to be published by Simon & Schuster.
The titbits that have dribbled out are interesting enough: how the reckless affair with Monica Lewinsky, conducted intermittently between late 1995 and early 1997, came when Clinton "just cracked" after political setbacks and the death of his mother. Then there is the hilarious account of how a drunken Boris Yeltsin, wearing only his underclothes, tried to hail a cab in the small hours to find a pizza, during a visit to Washington 1995. Mercifully for Russian/US relations, he was caught by Secret Service men.
Most fascinating is Mr Clinton's account, relayed by Mr Branch, of a bitter and at times "surreal" two-hour conversation with Al Gore, after the 2000 election. Mr Clinton purportedly contended that his vice-president could have won, had he allowed his boss to campaign in Arkansas and New Hampshire – both states where he was popular, both in the event carried by George Bush. A win in either would have made Mr Gore president, with obviously colossal implications for US, indeed world, history. But Mr Gore retorted that the Lewinsky scandal had been an impossible "drag" on his candidacy. To which Mr Clinton bitingly replied that if his Hillary could successfully run for the Senate from New York on their administration's record, why couldn't Al Gore have done the same?
The tapes of Mr Branch will undoubtedly lead to a best seller, even though Mr Clinton has major reservations. "I think it's fair to say he's nervous," the historian has said. "But he has enormous tolerance for honest criticism. I think he can take it raw, as long as he doesn't detect that it's done for malice."
But the real question is whether and when the original tapes will be made public, or at least available to scholars. In 2004, Mr Clinton published a best-selling autobiography My Life, for which he received a then record advance of $15m (£9m). But it is surely sanitised stuff alongside the contents of the tapes.
For future historians, they will be a treasure trove, as they try to unpick the mind and motives of a highly complicated, extraordinarily gifted man. Such unvarnished records are growing ever rarer, in an age of instantly deletable emails, when anything not deleted might end up as evidence for a prosecutor.
According to Mr Branch, the Clinton he heard was a more admirable individual than the glib and cynical "slick Willie" so often depicted. Like many liberals, Mr Branch initially thought his friend had betrayed the faith, as just another "member of this species called 'politician'," he told GQ. As for Mr Clinton's incessant pursuit of elected office, "I connected it to ambition. The notion that it came from a sense of idealism didn't rear up for me until I was able to watch him in the White House."