In a matter of days, the U.S. Department of Justice will release a redacted version of Special Counsel Robert Mueller’s report on Russian interference in the 2016 U.S. presidential election. It is tempting to believe that, at long last, Mueller will deliver the definitive account of Russia’s operation. But even after 22 months, 2,800 subpoenas, nearly 500 search warrants, and 34 indictments, there is reason to expect that Mueller and his team of attorneys will not have uncovered the full story. When it comes to covert foreign electoral interference, probes are rarely conclusive: key witnesses live abroad, lies pass as truth, and unanswered questions can stay that way for decades, sometimes forever.

For the past two years, much of the U.S. news media has been drawing parallels between the Russia investigation and the Watergate investigation, which produced damning evidence against President Richard Nixon and ultimately led to his resignation. But there is a far better historical precedent for Mueller’s investigation. In 1973, while the U.S. Congress was investigating Nixon, the West German parliament, the Bundestag, formed an investigative committee of its own. The committee’s purpose was to probe possible interference in a parliamentary vote of no confidence held in an attempt to oust Chancellor Willy Brandt.

The vote, which had taken place the year before, came at a pivotal moment in West German and Cold War history. Brandt had just negotiated reconciliation agreements with the Soviet Union and Poland as part of his conciliatory Ostpolitik. The conservative opposition in the Bundestag, strengthened by a series of defections from Brandt’s coalition over the treaties, called the vote of no confidence to prevent their ratification. With Brandt’s future uncertain, the attention of world leaders turned to Bonn. “This is the first time in the whole postwar history that anyone has attempted a vote of no confidence. It shows how weak [Brandt’s] government is,” Henry Kissinger, the U.S. national security advisor, told Nixon in a private conversation the day before the motion was held.

Almost everyone expected Brandt to fall from power. When he didn’t—247 lawmakers voted against him, two short of the necessary 249—suspicions immediately arose that someone, somewhere, had paid members of the opposition to abstain. “I knew that a couple of people were bribed in the vote,” Joseph Wippl, a former CIA operative who arrived in West Germany in 1974, told me. “But I didn’t know where the money came from.”

Neither the Bundestag nor the CIA could prove then what we can conclude today: East German operatives, on orders from Moscow, rigged the vote in Brandt’s favor. “We were a very good team and could count on each other and did what was necessary,” Horst Kopp, a retired East German spy, told me in Berlin. In our interview, Kopp was ready, even eager, to discuss what he called the greatest accomplishment of his decades-long career: the plot to preserve Brandt’s government. “There weren’t many who would have dared to attempt such an operation because it took years, cost a lot of money and the level of risk was high. But we prevailed.”

NOTHING NEW UNDER THE SUN

Russian President Vladimir Putin’s campaign to manipulate the 2016 U.S. presidential election included innovative tactics enabled by the Internet. But as the 1972 vote demonstrates, Putin did not invent the idea of covert electoral interference. “People who don’t know what they’re talking about refer to it as ‘unprecedented,’” John Brennan, the director of the CIA from 2013 to 2017, told me. In reality, from Washington to Moscow, policymakers have long hatched plans to sway foreign electoral processes, whether presidential races, referendums, or parliamentary votes of no confidence.

During the Cold War, the great powers lacked the digital tools that Russia harnessed in 2016. But they nonetheless manipulated elections to advance their interests. American and Soviet agents funneled money to their preferred political parties abroad. They also spread disinformation about specific candidates. During the 1976 U.S. presidential election, for example, Soviet agents sent major U.S. newspapers a fictitious FBI file alleging that Senator Henry “Scoop” Jackson, a Democratic candidate for president, was gay, in the hopes that they would publish it. (His career progressed uninterrupted.)

Beyond such attempts to manipulate the minds of voters, governments have sometimes carried out a bolder, riskier, type of electoral interference: altering the actual vote. All available evidence suggests that in 2016, despite hacking many of the United States’ voting systems, Russia did not tamper with the results. Forty-seven years ago, however, Moscow showed no such restraint. On the eve of West Germany’s vote of no confidence, the Stasi, East Germany’s state security service, changed ballots at the Soviet Union’s direction.

“We received a directive from Moscow…to do everything we could to keep Brandt in power as Chancellor so that the agreements could be ratified in the Bundestag,” Kopp recalled, an instruction confirmed by both Vasili Mitrokhin, the famed KGB archivist-turned-defector, in a book he co-authored in 1999, and Markus Wolf, the long-time head of the Stasi’s foreign operations, in a 1996 interview. Newly available evidence reveals that, after receiving the order, the Stasi paid two lawmakers in the opposition—Julius Steiner and Leo Wagner—to abstain. As a result, the vote failed, Brandt remained in office, and his treaties were ratified.

COLLUSION

The simplest aspect of investigating a covert electoral interference operation is often determining the motivation behind it. According to the U.S. intelligence community, Putin interfered in the 2016 election, in part, because Donald Trump took a more conciliatory stance toward Russia than did his rival, Hillary Clinton. Moscow made a similar calculation in 1972, when it supported Brandt, whose Ostpolitik had helped usher in an era of détente in the Cold War. The bilateral agreements he had negotiated with the Soviet Union and Poland, which promised economic relief for Moscow’s eastern bloc, stood no chance of passage without Brandt’s stewardship.

The Stasi fixated on Wagner and Steiner, the two lawmakers, because of their personal vulnerabilities. As with Russia’s social media disinformation campaign in 2016, which targeted millions of American voters based on their individual profiles, the Stasi played to the personalities of its targets. But unlike Russia in 2016, the Stasi lacked access to troves of personalized data profiles stored on the Internet, so they studied Wagner and Steiner through traditional espionage. Both men drank recklessly, partied excessively, and accumulated significant debts. Wagner spent up to 4,000 deutschmarks (the equivalent of $7,280 today) a night at bars in Bonn and Cologne. The Stasi noticed—unsurprisingly, given the reach of its network. “The Stasi was everywhere,” Admiral Bobby Inman, NSA director under Jimmy Carter, told me. Porter Goss, a CIA operative during the 1960s who later directed the agency, put it simply: “I feared the Stasi. They were thugs… They had files on everybody.”

The Stasi exploited Wagner’s and Steiner’s financial issues well before the vote of no confidence occurred. In need of money, Steiner began feeding intelligence to East German agents as early as 1970; Kopp recalled that Wagner did the same through a middleman, a Bavarian journalist who claimed to represent private companies but was in truth employed by the Stasi. Wagner “joined our cause in the early months of 1970 [but] he didn’t join thinking that we were the [Stasi] but under the false pretense…that we represented commercial and trading interests in the western world,” Kopp said. Benedikt Schwarzer, a grandson of Wagner who recently produced a short film about his life, believes that Wagner participated in the scheme to pay off his debts.

German prosecutors, investigating Wagner years later, found that he had been living beyond his means since the late 1960s, right around the time that Kopp said he began leaking internal information. Steiner and Wagner’s initial work, while passive, made the two men reliant on their benefactors. The Stasi had corrupted them slowly—a “classic” tactic of intelligence agencies across the world, according to Donald Gregg, who worked for the CIA between 1951 and 1982. “The goal at CIA was always to draw a source in and then put him in a position where he really couldn’t say no,” Gregg explained.

By April 1972, the Stasi had the relationships it needed to swing the vote of no confidence in Brandt’s favor. Already compromised, Steiner and Wagner had little choice but to do as their handlers wanted. Each received 50,000 deutschmarks ($91,000 today) in return for abstaining. “His debts, his position—everything was on the line in the vote,” Kopp said. “Without the money from us, he would have already been bankrupted.”

On the morning of the vote, Wagner, Steiner, and hundreds of other lawmakers took turns entering a private booth and either marking their cards “yes” or “no” or, to signify abstention, leaving their cards blank. All votes were anonymous. The president of the Bundestag announced the result: Brandt had survived, against even his expectations. Members of his coalition hugged. A few attempted to lift Brandt into the air. The news reverberated across the globe: “BRANDT DEFEATS MOVE TO OUST HIM,” blared the front page of the next day’s New York Times.

A foreign power can affect an electoral process—and alter the trajectory of a nation—with or without the cooperation of the person who benefits. No available evidence suggests that Brandt knew about the Stasi’s operation, although he later wrote in his memoirs that he suspected “that corruption had been at work during the run-up to the vote.” It would have been self-defeating for the Stasi to alert him to the effort: had Brandt’s involvement been uncovered, his legitimacy would have collapsed. In 1972, at least, it served Moscow’s interests to maintain Brandt’s ignorance.

COVER-UP

Brandt and his allies were not the only ones celebrating the outcome of the vote of no confidence. Just before the motion was held, East German leader Erich Honecker had privately claimed that Brandt would survive “not least with our support and thanks to our measures.” A few weeks later, in May, he bragged to Romanian leader Nicolae Ceauşescu about his government’s methods. “We took several measures to support the Brandt government shortly before the vote of no confidence,” he said. “This government is obviously more convenient for all of us.”

The Stasi’s operation worked only because it remained secret. Had it been uncovered while Brandt was still in office, his mandate would have suffered (as it did in 1974, when, ironically, a separate East German spy scandal prompted Brandt’s resignation). The Stasi ran a risk, then, in that it could not ensure the silence of Steiner and Wagner, whose self-destructive behavior rendered the lawmakers assets before the vote but potential liabilities after it.

About a year after the vote, in an interview with a West German newspaper, Steiner revealed that he had abstained. The admission attracted widespread attention, and the Bundestag formed a bipartisan committee to investigate. Reporters dubbed the inquiry “Watergate in Bonn.” Brandt’s allies, like some American politicians today, raged that the probe was little more than a ruse designed to undermine the victor. “The aim of the Steiner affair is to try to drag the Chancellor into it,” Horst Ehmke, one of Brandt’s senior advisors, complained in September 1973.

Luckily for the Stasi, the investigation soon stalled. The internal file the Stasi kept on Steiner notes that the investigators had “not determined whether there [were] any connections” between him and the Stasi. Only after East Germany dissolved did Markus Wolf admit that his men had purchased Steiner’s abstention; likewise, according to the KGB archives at Cambridge University, Steiner cast his ballot “on instruction” from the Stasi. And in a 1996 interview, Wolf revealed that the Stasi had bought a second, unnamed lawmaker.

The Bundestag committee failed to identify Wagner as the second abstainer, and he remained a force in parliament for several more years. In 1975, as a result of his debts, his colleagues forced him to relinquish his role as a parliamentary managing director. He left the Bundestag late the next year, but his relationship with the Stasi persisted. The Stasi’s file on Wagner, which lists Kopp as his supervising agent, contains 41 entries summarizing the intelligence he provided between 1975 and the mid-1980s.

Eventually, Wagner, like Steiner, stumbled into the spotlight. In 1980, when Wagner appeared in court on fraud charges, prosecutors discovered that he had received 50,000 deutschmarks from an unknown source in 1972, around the time of the vote. Twenty years later, a German newspaper reported that federal prosecutors suspected that the Stasi had paid him to abstain. Wagner, who perhaps still thought he had been informing for private trading companies, denied the allegations. He died a few years later. Only recently has Germany determined that the Stasi bribed Wagner. A German government report, published in 2013, more than 40 years after the vote, concluded that the Stasi, acting through its middleman, exploited Wagner’s “financial problems” to get him to abstain.

As analysts today attempt to make sense of electoral interference, the Stasi’s scheme, blessed by Moscow, sheds light on the roots of the practice. “Democracy is a procedure to change rulers,” the historian Timothy Snyder has written; the Stasi attacked just such a procedure and, therefore, the heart of a Western democracy. Unable to hack into the ballot box, Kopp and his team used human agents to manipulate the vote directly. Collusion with lawmakers was essential, as was secrecy. And in the Bundestag then, as in Congress today, an investigation into electoral manipulation swiftly devolved into partisanship, finger pointing, and distrust.

On the eve of the Mueller report’s release, the Brandt affair offers a discomforting lesson: it can take decades to pull back the curtain on covert electoral interference. Despite Mueller’s efforts, there is no guarantee that he has uncovered the full extent of Russia’s operation. If history is any guide, the odds were always against him.