For a time, Ted Kennedy kept Kevlar vests in his hall closet. He didn’t like to wear them, but the massive FBI files released Monday explain why he did when he had to.

More than 2,000 pages of files detail dozens (I lost count) of threats against his life. They peaked around the deaths of Robert F. Kennedy and Mary Jo Kopechne and his own presidential run in 1980. But the earliest cited by the FBI was in July 1962, before he was even a senator. The last mentioned in the files was in May 1985, after he had abandoned the quest for the White House.

It is intriguing that the files show no FBI effort to investigate Chappaquiddick and Kopechne’s death when Kennedy drove off a bridge in 1969.

What you can’t tell from reading the bureaucratic detail is which of those threats amounted to real danger. (There are a few that seem comical, like a Vermont man who explained that he liked the mental institution where he was confined, and figured his threatening letter would keep him from being discharged.) But when that letter or the others arrived, Kennedy couldn’t tell which were real and which were not. So he took them seriously.

There was a certain fatalism about it. One night in 1969, he told reporters that if he ever ran for president, “They’re going to shoot my ass off the way they shot off Bobby’s.” But after considering retirement from public life after Bobby’s death, he decided instead “to pick up a fallen standard” and carry on in the Senate, and in 1979, to run for president, wearing those awkward vests.

• Samuel P. Jacobs: What’s in the Kennedy Files? The FBI’s reaction to the threats reads as prompt and professional. It was not lack of effort by the bureau that led assistant United States attorneys—in Washington, or Boston or elsewhere—to drop cases after concluding there was no prosecutable offense because whoever made the threat had no realistic ability to act on it. That was the judgment on one 1972 letter-writer who said “Ted Target #3 … Get Your Pine Box Ready… Bullet in Your Neck.” A similar view was taken in 1975 when a postcard asked, “When Should I kill you” or “get someone else to do it.” A former Soledad Prison neighbor of Sirhan B. Sirhan, Robert’s assassin, told the bureau in 1977 that Sirhan had offered him $1 million to kill Ted; he said he refused, and that appears to have been the end of it.

But the bureau does not always come out of the release shiny and pure. In 1961, Kennedy took a Latin American trip to burnish credentials for a 1962 Senate bid. The FBI checked out the background of his companions on the trip, noted his request for a meeting with leftist Mexicans, and then copied his diary after he left it on a plane. The bureau then sent the diary to the White House, not to Attorney General Robert Kennedy.

When he was elected to the Senate in 1962, bureau files were searched and higher-ups advised about his expulsion from Harvard for cheating, about an unidentified North Carolinian who telephoned Kennedy around the time he was sent to prison for larceny, and about Kennedy's 1956 request for an Egyptian visa. Why the FBI considered the president's youngest brother a subject for this scrutiny is not in the files.

There is one amusing interaction between Kennedy and J. Edgar Hoover. After nearly dying in a plane cash in 1964, Kennedy compiled a book of reminiscences of his father, Joseph P. Kennedy. He asked Hoover to contribute, and the director did so with fulsome praise for Joe Kennedy. He hailed Joe’s dubious tenure as ambassador to Great Britain and his generosity in promising a huge campaign contribution if Hoover ever ran for president. Kennedy and his aides deleted that material. A couple of innocuous paragraphs are all that appeared in the privately printed book, The Fruitful Bough.

There really are no revelations in the release. It is intriguing that it shows no FBI effort to investigate Chappaquiddick and Kopechne’s death when Kennedy drove off a bridge in 1969. The FBI did get a heads-up from the Edgartown police chief, Dominic J. Arena, but the other 76 pages in that file are all copies of newspaper articles. Considering President Nixon’s paranoia about Kennedy, one might have expected him to press the FBI for dirt. But perhaps Hoover just believed what he told people who wrote and demanded that he do something about the case: “There is no indication that the death of Miss Mary Jo Kopechne involved the violation of any federal law within the jurisdiction of the FBI.”

The fact that Kennedy faced death threats is not news, either. Kennedy and his staff never talked about them, but reporters knew they were there. What we did not know was their frequency, sometimes several times a month. The constancy of threat offers one more measure of the courage that underlay the determination he hailed as he closed his memoir, True Compass, with a chapter titled “Perseverance”:

“[T]he greatest lesson I have learned: If you persevere, stick with it, work at it, you have a real opportunity to achieve something.”

Adam Clymer is a former Chief Washington correspondent of The New York Times and author of Edward M. Kennedy: A Biography.