Stefan Halper: Cambridge professor, former middling aide to Gerald Ford, Ronald Reagan and George H.W. Bush. Now, apparently, the confidential source for the FBI’s investigation into the Trump campaign. That isn’t a résumé to shrug off.

But there is one thing my reporting has found he did not do: He was not involved in stealing President Jimmy Carter’s briefing books during the 1980 presidential election. Halper did obtain a memo from the Carter White House advising the incumbent how to deal with Reagan, but this was long before the debate, and there is no evidence Reagan ever saw it or was told of it. (The Carter White House leaked profusely, thanks to former Nixon and Ford administration civil servants who were still there.)

Since Halper’s name surfaced in connection with the Trump investigation, several news sites and hosts, such as Bill O’Reilly (who has gotten things wrong with Reagan before) and Mary Kay Linge at the New York Post, have been reporting, incorrectly, that Halper was involved in and responsible for the so-called Debategate scandal, which rocked the early Reagan administration. Just before the only debate between incumbent Carter and former governor of California Reagan, Carter’s briefing books, detailing Reagan’s policies and talking points, were inexplicably stolen from the White House. They somehow ended up in the Reagan camp.

The implication of the scandal, especially when it first broke, was that Reagan won the debate — and perhaps the presidency itself — because of stolen property. The truth is in my book on the 1980 campaign, “Rendezvous With Destiny.” I painstakingly pursued the facts about the stolen briefing books for months, but I had an advantage: I knew Paul Corbin, who was a friend of mine. And Corbin stole the briefing books and gave them to his new friend, Bill Casey, Reagan’s 1980 campaign manager.

Some on the right, including Roger Stone on the “Laura Ingraham Show” and Rush Limbaugh on his own, are quick to assume that Halper was guilty of the Carter theft, and that because he is now involved in a current presidential election scandal, that must mean he was also guilty in the past. Maybe that’d be his modus operandi. Some on the left, as well as some in the media, are quick to buy into this falsehood and a means of bashing Reagan once again.

But the briefing books weren’t stolen by Halper. You can thank a lifetime Democrat and labor organizer and Kennedyite for that.

When Corbin died in 1990 at the age of 75, his obituary in the New York Times was simple, about a thousand words long. But behind the political career was a man deeply and anonymously involved in the great campaigns and causes of his era. He was a card-carrying member of the Communist Party, yet he also engaged in business dealings with Sen. Joe McCarthy. He was a lifetime Kennedy family retainer who played in a weekly poker game with a bunch of conservatives including myself. He was a liberal who hated Carter. He was a man of many contradictions and few principles.

Corbin had a history with the FBI. The bureau opened a file on him in 1940, soon after he entered the United States from Canada, and eventually accumulated over 2,000 documents. He was often under active surveillance by FBI field agents.

The released FBI files were telling: He was a cheater. He enjoyed swindling friends and enemies alike. “He was a rascal. He created trouble. He upset people . . . . He didn’t respect people,” said Kathleen Kennedy Townsend. He entered from Canada illegally during the 1930s, was deported several times and sneaked right back in. In 1939, he abandoned his family in Brooklyn, moving to the Midwest. Five years later, he divorced his first wife; that same day, he married another woman.

He worked for both the American Federation of Labor and Congress of Industrial Organizations before the two merged, but he also worked for unions kicked out of the AFL-CIO for their communist leanings. He denied it, but both the FBI and old friends believed he was a socialist if not a full-blown communist.

He was also extremely upset with the Carter administration by late 1980. A family loyalist who had worked on presidential campaigns for John F. Kennedy and Robert Kennedy, Corbin had an informal role in Ted Kennedy’s failed run that year, to simply “stir up trouble,” according to a friend, Adam Walinsky. Once Kennedy was out, Corbin, always thinking of the restoration of Camelot, looked ahead. He’d work for Reagan, he decided, to defeat Carter, and wait for 1984 for a Kennedy revival. Corbin was called “Uncle Paul” by RFK’s children, and he became a Catholic because of his deep admiration for the Kennedy family, and he was a retainer to various family enterprises for years.

On Oct. 25, 1980, just three days before the only debate between Reagan and Carter, the president’s briefing books — one on foreign policy, one on domestic policy and one for Vice President Walter Mondale — went missing. And they ended up in Reagan HQ. Corbin that same day received $1,500 from William Casey, Reagan’s campaign manager. Several days later, he picked up another “research” check after being with Casey. Jim Baker told me he knew that the briefing books were there. Even Stefan Halper knew it, and admitted as such in an interview to me in 2007. So did many others in the Reagan campaign.

Reagan did not, though. “It seems strange to me,” he had said in a news conference, “that since I was the debater, no one on our side ever mentioned to me anything of this kind, or that they had anything or told me any of the things that supposedly were in there.” At any rate, the books were simply a recitation of Reagan’s old radio commentaries and columns and speeches. Reagan knew what he’d said and written, and his handlers dismissed the books as meaningless.

The rest, they say, is history. Reagan won the debate hands down and ended up winning 44 of 50 states a week later with over 50 percent of the popular vote.

The news of the stolen briefing books did not surface until 1983, with the publication of Time columnist Laurence Barrett’s “Gambling With History.” It immediately took everyone by storm. Congress ordered an investigation, which cost half a million dollars, and interviewed everyone under the sun. Corbin, of course, denied it, under oath. One congressman, Donald Albosta (D-Mich.), however, noted that Corbin’s testimony was bunk: “He denies everything . . . doesn’t even know his own name.”

The committee concluded that sometime the day or the night before the books were noticed missing, someone — it was not decided who, officially — took the books off national security adviser Zbigniew Brzezinski’s desk. Albosta, who headed the House committee, was of the impression that it was Corbin. “Corbin has been stated by several people as the one who delivered the material to [Bill] Casey,” he had told the Times.

Corbin never admitted to stealing the briefing books, but to his poker buddies, he intimated as much. He told Tim Wyngaard, a Wisconsin political friend of Corbin’s, that he had stolen the books; Wyngaard, in turn, told Richard B. Cheney, his former congressional boss. Casey told the congressional committee investigating the theft that Corbin had given him “some material.” And Baker told the same committee that Casey had told him that Corbin “might have been a source” on the stolen briefing books. Corbin, of course, lied when he testified to the congressional committee but lying to federal investigators was old hat for the old political agitator. At the time, Newsweek wrote his “reputation for veracity is uneven.”

There was an actual conspiracy both within and outside of the White House to bring Carter down. This included Reagan staffers and White House staffers who, having worked under Ford and Nixon, did not like Carter. And for Corbin, there was a personal stake, too: He wanted revenge on Kennedy’s behalf.

Halper did not. At the time, he was just a low-level aide to the Reagan campaign. Nothing more, nothing less. Corbin, however, hoped to tear down the Carter White House and, in its ashes, plant Kennedy’s flag again. On the first phase, he succeeded. On the second, he failed.

One thing is for sure: Had Reagan known of the purloined papers, he would have been furious and would have directed they be sent back to Carter with a note of apology and would have refused to look at them.

In 1980 — at least for Reagan — there were moral impossibilities.

Scott Mauer contributed research and reporting for this article.