Historians of the far future will be puzzled by many of the events in the Trump presidency, perhaps none more baffling than the bizarre cult that sprang up around Robert Mueller, the special counsel who from 2017 to 2019 investigated Russian election interference. During those years, there was a significant number of liberals who thought Mueller was the savior who would deliver America from Trump. As The New York Times noted shortly after the Mueller report was filed, fans of the special counsel “elevated Mr. Mueller, a former F.B.I. director, into an anti-Trump cultural icon, complete with T-shirts, scented candles and holiday-themed songs like ‘We Wish You a Mueller Christmas.’”

Saturday Night Live did a running series of skits featuring Alec Baldwin as a cowering Donald Trump living in fear of Mueller, played by Robert De Niro as a tough, laconic, and menacing cop. Two prominent online “Resistance” liberals, Ed and Brian Krassenstein, produced a children’s book that, according to The New York Times, “depicted Mueller as a superhero—complete with a shirtless, muscular pose.” (The Krassensteins responded to mockery of their book by claiming it was a “parody.”)

The Mueller cult now looks ridiculous—and not just because the special counsel came to the ambiguous conclusion that the Trump campaign welcomed Russian interference in the 2016 election but there was insufficient evidence of a criminal conspiracy. Rather, what makes the Mueller cult feel hopelessly naïve is the strong evidence that has emerged that the special counsel, far from scaring Trump, was cowed by the president.

Former prosecutor Andrew Weissmann, who helped oversee the investigation into onetime Trump campaign head Paul Manafort, reflects on the failure of the Mueller team in his forthcoming book, Where Law Ends: Inside the Mueller Investigation, set to be released next week.

As New York Times reporter Charlie Savage details, the new book shows a number of significant areas where the Mueller investigation pulled its punches, notably the fact that a hush fund used to pay off adult film actress Stormy Daniels received, according to Weissmann, “payments linked to a Russian oligarch.” Another significant episode involves the issuance of secret subpoenas to Deutsche Bank to uncover details about possible Ukrainian funds sent to Manafort. Although the subpoenas were supposed to be secret, news of them leaked to the White House, which strenuously opposed this line of inquiry. The White House seems to have feared that loans from Deutsche Bank to the Trump Organization could also be targeted for investigation. The upshot of the dispute was that Mueller’s team retreated from any inquiry into Deutsche Bank’s ties to Trump.

“Had we used all available tools to uncover the truth, undeterred by the onslaught of the president’s unique powers to undermine our efforts?” Weissmann asks, “I know the hard answer to that simple question: We could have done more.”

The reasons for this failure to mount a full investigation are manifold. The Manafort team was under constant attack not just from the White House but also from right-wing media outlets like Fox News. This seems to have given some of them, notably Mueller’s deputy Aaron M. Zebley, pause. Mueller, a Washington fixture, proved incapable of standing up to the Republican establishment that has been his lifelong milieu.

Reviewing Where Law Ends for The New York Times, Jennifer Szalai observes that Weissmann finds “Mueller’s fundamental flaw“ to have been “a persistent faith in a Justice Department headed by his old friend William Barr. The Mueller team had meticulously laid out their findings in their 448-page, antiseptically worded report, only to be ‘blindsided’ by Barr’s four-page self-styled summary, which Weissmann depicts as a nakedly cynical distortion of the truth: ‘We had just been played by the attorney general.’”

The cult of Mueller was based on the dubious idea that a Republican and lifelong member of the Washington elite would pursue a relentless and scorched-earth investigation into a GOP president. This belief, in turn, rested on an idealization of federal law enforcement, seen as uncorrupted and rigorously loyal to the law. The liberals who joined the Mueller cult gave as much credence as any conservative in the cultural myths J. Edgar Hoover created in the early 20th century to legitimize the FBI. These myths paint federal lawmen as uniquely worthy: crew-cut upholders of justice who could be trusted more than politicians.

This is not the first time liberals have overestimated the ability of law enforcement to check political corruption. The Watergate scandal hinged on the persistent probing of special prosecutor Archibald Cox, whose firing by the Nixon White House itself became part of the scandal. In the wake of Watergate, successive political scandals have seen liberals look for a new Archibald Cox, a prosecutor or law enforcement hero who could fight Republican corruption. The role has been variously played by Lawrence Walsh (during Iran/Contra), Patrick Fitzgerald (during George W. Bush’s presidency), and an array of figures in the Trump era: Sally Yates, James Comey, and Robert Mueller.

Some of these figures have done their job well. Walsh’s investigation of Iran/Contra, done in the face of a hostile administration, was exemplary. But it’s notable that they all yielded nugatory results. Watergate remains the exception: a scandal that resulted in a president resigning. In every other subsequent presidential scandal, including those involving Bill Clinton, the commander in chief was able to put up a successful blockade, relying on either a promise of pardons, deference from investigators, or partisan loyalty from congressional allies.

Prosecutorial liberalism is a fantasy, one that weakens other ways of checking presidential corruption. The more figures like Mueller are idealized, the less pressure there is on Congress to fulfill its constitutional duty to provide oversight of the Executive Branch. It also absolves citizens of the duty to organize protests when, as with Trump, a president is demonstrably corrupt. The Mueller investigation has been combined with a Congress that impeached Trump on the narrowest possible grounds and avoided the difficult work of enforcing subpoenas in the face of White House stonewalling. But to pick a fight with Trump on these grounds, congressional Democrats would have to take real political risks, including shutting down the government if the White House remained recalcitrant.

Would it be worthwhile to shut down the government, with the risk of alienating many voters, to challenge Trump’s corruption? That is a thorny political question, with no easy answer. But it’s a question congressional Democrats have been able to avoid because the party’s liberal base was too focused on the false promise of Mueller to push for congressional action.

Prosecutorial liberalism is a safety valve that releases popular anger while allowing the status quo to continue unchanged.

The Trump era has tested the health of the American political system, and it’s impossible to offer a cheering diagnosis. Even if Trump is defeated in November, he’s shown how much corruption a president can get away with so long as he has the unwavering support of his own party and an opposition that is unwilling to risk a government shutdown.

Political corruption is ultimately more a political problem than a legal one. It thus requires a political solution. In theory, Congress could assert itself to check the imperial presidency that allowed Trump to get away with so much. It could require presidents to be open about their finances; it could formalize the principle that congressional subpoenas must be obeyed (with penalties for disobedience); it could end the principle that presidents can’t be charged for their crimes while in office. But there’s little evidence that Democrats are interested in any sweeping rollback of the imperial presidency. America is likely to remain a nation whose political system can’t restrain presidential corruption. This leaves the United States ripe picking for future Trumps.