Who approved the Watergate break-in? Let’s go to the tapes.

On the 50th anniversary of the Watergate break-in, one great mystery remains: Who was the top official to approve the illegal entry into the Democratic National Committee headquarters? An obscure tape provides an answer.

It is not one of the famous White House tapes — the ones that helped end Richard M. Nixon’s presidency — but instead an audio diary recording dictated by Nixon’s chief of staff, H. R. “Bob” Haldeman. And it points the finger squarely at one of Nixon’s most trusted advisers: campaign manager and former attorney general John Mitchell.

The Haldeman tapes have been largely overlooked by historians, who have cast doubt on whether Mitchell knew about the break-in. In his 2008 Mitchell biography, “The Strong Man,” James Rosen, now chief White House correspondent for Newsmax, argued that Mitchell not only did not order the break-in but that he didn’t know about it until after the arrests in June 1972.

More recently, Garrett Graff concluded in “Watergate: A New History,” published this February, that existing accounts of Mitchell preapproving the break-in are likely "wrong.”

But the Haldeman audio diary states clearly that Mitchell did approve the operation; he confessed as much privately to Haldeman and White House Counsel John Dean on March 28, 1973. Haldeman recorded the admission late that night just before going to bed.

The recording is the kind of evidence that lawyers rely on all the time in criminal cases. And, fortunately for history, it is of high fidelity — amazingly intimate all these decades later, as if you are sitting with Haldeman in his home study as he dictates.

Mitchell’s apparent authorization of the break-in places the operation at the heart of Nixon’s inner circle. Mitchell was one of Nixon’s only close friends. He hired Nixon as a lawyer at his firm during Nixon’s wilderness years after failed campaigns for president in 1960 and California governor in 1962. He encouraged Nixon to try for the presidency again in 1968, then ran his campaign. Mitchell served as attorney general in Nixon’s first term before heading his reelection campaign in 1972.

In other words, according to Haldeman, the highest-ranking person to approve the Watergate break-in was the man who orchestrated Nixon’s political career.

Here is how Haldeman started his diary entry on the night of March 28:

The speech referred to was Nixon’s final address to the nation on Vietnam, after he ended U.S. involvement in the war in January 1973.

Watergate, however, was beginning to consume his presidency.

Just a week earlier, on March 21, Dean had warned Nixon that there was a “cancer growing on his presidency.” The Watergate burglars and their bosses, E. Howard Hunt and G. Gordon Liddy, were set to be sentenced March 23 before Judge John Sirica. Dean told Nixon that Hunt was demanding more “hush money” in advance of the hearing — lawyer fees and family support during his expected incarceration. Dean predicted it would take $1 million to fund such a blackmail request. Nixon responded he knew where he could get the money — in cash.

[How the Watergate scandal broke to the world: A visual timeline]

On March 23, one of the burglars, James McCord, delivered a letter to Sirica stating that “others involved in the Watergate operation were not identified during the trial.”

Rumors and allegations flew, and McCord started naming names. Getting only some of the details right, McCord cited Dean and deputy campaign director Jeb Magruder as the “others” he believed were involved in planning and executing the Watergate operation.

Magruder had presented the final break-in plan to Mitchell in late March 1972, after which Magruder asked his assistant to tell Liddy it had been approved. Dean had not been involved in that meeting but had participated in earlier meetings in Mitchell’s office with Magruder, in January and February, where Liddy presented intelligence plans that initially went nowhere. (Disclosure: For 11 years, I have taught a legal ethics seminar together with Dean, based on the Watergate saga.)

Mitchell, Magruder and Dean had to get their stories straight. Haldeman called all three to the White House on March 28, 1973.

Mitchell and Magruder pressured Dean to support their previous grand jury testimony that they had met only once with Liddy and that the meeting had not involved intelligence, but campaign finance issues. Dean refused, recognizing he would perjure himself if he agreed.

That night, Haldeman faithfully recorded his diary entries for the day.

Haldeman saw the discrepancies in Mitchell, Dean and Magruder’s accounts of their meetings with Liddy as potentially devastating. He likened the situation to the Alger Hiss espionage investigation Nixon conducted as a congressman, where rolls of film containing secret State Department papers were discovered in a hollowed-out pumpkin, which later helped convince a jury that Hiss was guilty of perjury.

As he continued his monotone dictation, Haldeman said the “drip, drip, drip” of Watergate had taken a toll on Mitchell. The pressure that started building the summer before, with the break-in and Mitchell’s subsequent resignation from the campaign, was now boiling over, sending Mitchell into a deep personal crisis.

Finally, Haldeman cut to the heart of the matter. He reported that Dean, who had participated in the coverup following the arrests of the burglars, said Mitchell and Magruder had both confessed to him that they “signed off” on the break-in. Dean thought they should come forward and take responsibility, while the coverup could somehow be “worked out.” Haldeman also recorded that in a separate meeting, Mitchell had admitted to him that he approved the Watergate plan.

This entry has all the hallmarks of credibility: a contemporaneous statement, recorded by someone who kept an audio diary as a matter of a regular business activity, containing damning admissions for everyone involved.

Judges frown on hearsay evidence, but this diary entry would almost certainly be admissible in federal court. Regular business records carry a level of trustworthiness. Similarly, admissions against interest are not defined as hearsay because people generally do not make statements damaging to themselves unless they believe they are true.

When presented with this evidence, Rosen, the Mitchell biographer, called it “inconclusive at best” and argued that the “project” Mitchell approved might have been “the overall intelligence-gathering operation that Liddy had pitched, not a specific operation at the DNC.” (Graff, the other author who questioned Mitchell’s role, declined to comment.)

There is some ambiguity in Haldeman’s language, but we know from multiple taped conversations from the spring of 1973 that Mitchell was presented in advance with the full scope of the operation, which included the break-in. We also know from these same tapes that Mitchell read transcripts of intercepted DNC calls from the first Watergate bugging in early June 1972 — making clear he knew about the bugging before the burglars were arrested June 17, and bolstering the other evidence that he was in on the plot from the start.

Perhaps Haldeman’s March 28 recording has been overlooked because of the sheer volume of the Nixon tapes and the density of Haldeman’s diaries — as well as the fact that it wasn’t made public until 1994, long after Nixon had been driven from office. But history should accurately record such critical admissions. Watergate got out of hand because Nixon couldn’t let Mitchell, his friend and mentor, take the fall. In an early White House tape, Nixon approved the coverup, fearing that admitting wrongdoing “would destroy” Mitchell.

This story has been updated to clarify Garrett Graff’s position on Mitchell’s role in the break-in.