Donald Trump has, as of the moment I write this, made 8,158 false or misleading claims since becoming President. He began by averaging five a day, but his daily score is now into the double figures and accelerating. Anyone who started out thinking he was just over-exuberant has had to reconsider. Falsehoods are a deliberate weapon in his political arsenal, and he has inspired a surge in fabrications from other leaders all over the world.

Politicians have always lied, but it has been generations since any did it like this. Glenn Kessler, who runs the Washington Post’s Fact Checker blog, has documented untruths for the best part of a decade, and says he is being challenged like never before.

In the United Kingdom where I live, Boris Johnson—a leading Brexit supporter who served as perhaps the worst Foreign Secretary in British history for two long years until last July—famously whipped up anti-immigration suspicion in the days before the referendum vote by spreading the false claim that Turkey was due to join the European Union. In January, he denied ever having done so, thus lying about having lied, and did so as brazenly as ever. He has not yet lied about having lied about having lied, but it is surely just a matter of time.

Vladimir Putin has turned lying into something of an art form, a denial of reality that is so brazen that it is almost impossible to tackle. There are no Russian troops in Crimea—“but, but those are Russian troops and they’re in Crimea”—there are no Russian troops in Crimea. A child has his hand in the cookie jar, is surrounded by crumbs, is smeared in chocolate, and yet denies having ever been in the kitchen. Even the most level-headed parent would be flummoxed.

Journalists who are accustomed to providing balance by reporting both sides of a debate—“he says taxes should be 20 percent to boost growth; she says taxes should be 70 percent to fund healthcare”—have always relied on the assumption that everyone is speaking in good faith. That assumption was always questionable, but now it’s downright dangerous. So, how does public discourse survive the phenomenon of politicians who lie strategically, who insist an inauguration crowd was the biggest ever, and who keep insisting that it was, when anyone with eyes can see that it wasn’t?

It is a tough question. As Peter Pomerantsev observed in his book on how the Kremlin has undermined the very concept of truth, when “nothing is true, everything is possible.” Political power increasingly belongs to the persuasive, not to the accurate. Voters prefer what they want to what they need, and lavishly reward those who will give it to them.

This is not a sustainable long-term strategy for government, to say the least. No matter how much liars bluster or charm, two plus two will always equal four; gravity will eventually catch up with Humpty-Dumpty. But by the time the egg hits the floor, the men who pushed him will be long gone. They are to society what pre-2007 bankers were to the economy.

There is much debate about what can be done about this. Should Facebook invest in fact-checkers? Should web apps flag websites known to propagate falsehoods? Should media interviewers call out politicians more robustly when they state something false? Should everyone subscribe to more news organizations, so journalists can be employed, rather than laid off? Yes, of course, to all of those things—but it still isn’t enough.

This is why it is so interesting to read Elise Bean’s argument for “robust, bipartisan congressional investigations” in her book Financial Exposure. Such investigations may not save the world, but they can give profound assistance to whoever eventually does. She knows this to be true because she’s been there, seen it, done it, and written it up in a book that details her time working for Senator Carl Levin at the Senate’s Permanent Subcommittee on Investigations (PSI).

The power of Congress to investigate arises from the magnificently named Teapot Dome scandal of the 1920s. The then-Interior Secretary had taken bribes in exchange for transferring valuable oil reserves to private companies, and Attorney General Harry Daugherty had failed to investigate. When Senators took that task upon themselves, Daugherty’s brother refused to appear before them to give evidence. They issued a subpoena, which he ignored. The case over whether he could be compelled to appear before them went to the Supreme Court, where justices sided with the Senators by 8-0, ruling that “the power of inquiry—with process to enforce it—is an essential and appropriate auxiliary to the legislative function.”

This case, McGrain v. Daugherty, gives members of the two Houses of Congress powers that are the envy of their international peers. These powers are not unlimited (Congress cannot look into individuals’ “private affairs” if there is no legislative purpose), but they are extraordinarily broad.

Sometimes those powers have been abused, such as with the unhinged hunt for Communists conducted by Senator Joseph McCarthy in the 1950s. Sometimes those powers have been used irresponsibly, such as when Republicans and Democrats dueled over whose party had behaved worse in the 1996 presidential election, a contest with remarkable resonance today. (“Questions included whether foreign money had influenced the outcome, whether the White House had broken any laws by selling political access to big campaign contributors, and whether loopholes in federal campaign finance laws were allowing campaign contributions to corrupt American politics,” Bean notes.) That inquiry produced two different reports, totaling 9,000 pages, with radically different conclusions that did little but confirm public frustration with politicians.

Even so, when congressional investigative powers are used correctly, proportionately and with due care for the considerations and concerns of both political parties, they have unearthed more secrets of the powerful and unscrupulous than almost anything else on earth.

PSI has an honorable history of investigating complex financial issues, including organized crime, fraud, offshore banking and other skulduggery. Investigations by the PSI helped bring about the Racketeer Influenced and Corrupt Organizations (RICO) legislation of 1970, and the world’s first laws on money laundering in 1986.

Financial Exposure is structured chronologically, and is not so much a story as a narrative. Each investigation took up months or years of Bean’s time, and each chapter is devoted to a single investigation. The book is well indexed, clearly written, and will be an extremely useful resource for future historians looking into the causes of the remarkable dysfunction that has afflicted Congress over the past few decades. They will perhaps be most struck by the contrast between how Congress works now and how it worked then, when PSI staffers from both parties would routinely get together after hours for drinks. “PSI managed to create an island of sanity, bipartisanship and mutual respect where we could conduct meaningful oversight,” Bean writes.

The publications that PSI has produced over the years constitute a priceless resource for anyone investigating the seamier side of the world economy. When I was researching my book Moneyland and wanted to know how the worst offshore banks had operated in the 1990s, I could turn to a PSI report into the Cayman Islands and find all the details I needed. When I wanted to see how Citibank had helped a succession of politicians from poor countries steal billions, again, it was all detailed by PSI. U.S. prosecutors have a long, rich and distinguished tradition of prosecuting fraud and corruption offenses, so these probes are not taking the place of criminal proceedings. Instead, they are complementing them, providing the context against which the crimes took place, and doing so in a way that anyone can rely on.

The hope of course was that the investigations would expose wrongdoing, inform legislators and inspire new bills that would close the relevant loopholes. Things did not always work out that way: After the Citibank report, Senator Levin co-sponsored a bill to toughen anti-money laundering regulations, but it died in the Banking Committee chaired by a Senator from Texas, which was home to many banks that had no intention of revealing the origin of their capital. The same thing happened, dispiritingly, to proposals to impose transparency on the ownership of U.S. corporate structures, with Levin’s efforts dying in the Homeland Security and Government Affairs committees. When the products of PSI’s work did turn into legislation, however, the impact could be stunning.

For example, after the attacks of September 11, 2001, it became clear how open the U.S. financial system had been to money laundering by terrorists. This generated support for an anti-money laundering bill Levin had proposed months earlier, which passed as part of the Patriot Act despite strong opposition from the banking industry. “It addressed virtually every one of the problems identified in our three-year money laundering investigation. It was an oversight triumph,” Bean writes.

Sometimes investigations also led to criminal probes, such as those into accountancy giant KPMG’s “tax shelters” that allowed companies to minimize their taxes. KPMG had ignored PSI’s subpoena, after a whistleblower brought evidence that it had been breaking the law, but gave in when news of its stonewalling leaked. KPMG’s auditors had sold tax shelters to the very companies they audited—in essence, they were marking their own homework—and the greater a tax loss the product created, the more KPMG got paid. It was a scandal of the most sordid kind. There was always an aspect of theater to PSI’s proceedings, since they culminated in witnesses being grilled live on television, and that was certainly true here. Levin asked one KPMG partner the same question repeatedly until he finally admitted the firm had sold tax shelters to its clients, producing incendiary news headlines.

It was a clear example of corporate criminality, so PSI passed the file to the Department of Justice, which eventually forced KPMG to admit to helping its clients dodge $2.5 billion worth of taxes, and to pay a then-record fine of $456 million. Investigations also helped lead to criminal proceedings against the businessmen Sam and Charles Wyly, who also ended up handing over millions in dollars in fines, and against the Swiss banking giant UBS. Whistleblower Bradley Birkenfeld brought PSI evidence of UBS’s misdeeds from his own spell at the bank, and the ensuing report helped lead to DoJ action that cracked open the fortress of Swiss banking secrecy.

Financial Exposure is full of insights into the huge financial impact of tiny quirks of banking legislation—“Subpart F” alone cost the Treasury billions upon billions of dollars—and the lobbying industry that springs up to defend them if they’re threatened. Multinationals went to great lengths to deny PSI the information it needed to probe their affairs, and often won the support of Levin’s fellow Senators in doing so.

Perhaps the most important lesson from the book, however, is the evolution in how Senators responded to corporations, and the subjects they therefore chose to investigate. In Bean’s telling, Levin himself was indifferent to the political consequences of his investigations, and happy to probe wrongdoing wherever it took place. But other Senators were not so indifferent.

This was seen first with Apple, when PSI looked into its tax arrangements. As a supporter of many Democrats, Apple was well networked in Washington. It was “cagey and slippery” in its dealings with PSI staff, Bean notes, while working as hard as it could to get Levin—and ranking Republican John McCain—to back off. McCain and Levin were independent-minded enough for the deflections not to work, but only in this instance. When it was time to investigate Caterpillar, times had changed.

“Our Republican counterparts had taken an internal drubbing after the Apple hearing. The McCain staff let us know that multiple Republican offices had contacted them to complain about their boss’s pro-tax stance and his working so closely with Senator Levin . . . they did become notably less enthusiastic about investigating corporate tax dodging,” Bean notes. When PSI functioned correctly, it was because everyone had the same interests—holding the powerful to account, and exposing their wrongdoing—even if they differed in their views about what to do about it. But with an increasing number of Senators more interested in helping the powerful than in upholding the law, that calculation came under increasing strain.

When Levin left the Senate in 2015, after more than three decades in office, he had overseen some of the most important investigations in congressional history, and worked as hard as anyone to maintain trust and respect across the aisle. But even fortnightly Manhattans and mutual goodwill could not hold back the tide of rancor and hostility that has spread through Washington. With ever more investigative effort focussed on the misdeeds of President Trump’s inner circle, and with even Republicans as outspoken as McCain unwilling to stand up for their principles in the face of corporate lobbying, the golden age of bipartisan oversight may be behind us.

Bean’s book is written carefully and cogently, in a style that could barely be more different than Trump’s ill-tempered, ill-considered, ill-spelt tweets. She stands for a different approach to running Washington, one that I sincerely hope will return in my lifetime. “Robust, bipartisan congressional investigations [are a] . . .  precious American heritage that should be respected, nurtured and celebrated,” she concludes.

From the perspective of an outsider, congressional oversight hearings are a remarkable expression of U.S. democracy, and one that I am delighted to have seen spread to Britain and other democratic countries. The British politician Margaret Hodge was inspired by Levin to expose tax dodging by Starbucks and other multinationals, and, although, committees in the UK Parliament lack the resources of their counterparts in Washington, they have managed to conjure up some of the theatrical appeal of the originals.

At a time when the influence of money in politics is reaching proportions unprecedented in living memory, it is crucial that politicians act as tribunes of the people in the way that Levin did. This is particularly true since so many members of the new generation of populist leaders hide their wealth using the same kind of tricks that Levin went to so much trouble to expose. When a street hustler does something amazing with his right hand, you can be pretty sure he’s robbing you with his left.

Careful investigation combined with publicly holding the powerful to account will be a crucial component of all future efforts to push back against the declension of democracies into oligarchies, and our legislatures into rubber stamps for the wealthy. Bean’s book is a primer for anyone keen to join that fight.