Then-FBI Director James B. Comey in March 2017 and President Trump in June 2017. Comey says in a book being released April 17 that Trump reminded him of a mafia boss who demanded absolute loyalty, viewed the entire world as being against him and lied about everything. (Nicholas Kamm/AFP/Getty Images)
A. Brad Schwartz is a doctoral student in American history at Princeton University and a co-author (with Max Allan Collins) of "Scarface and the Untouchable: Al Capone, Eliot Ness, and the Battle for Chicago ."

Americans are eagerly awaiting Tuesday’s release of former FBI director James B. Comey’s explosive memoir, which has reportedly presold nearly 200,000 copies. Comey, who investigated the mafia as a prosecutor in New York, compares President Trump to a Mob boss in the book — a comparison others have also run with. Michiko Kakutani, in her review for the New York Times, pushed the analogy further, likening Trump and Comey to the most legendary gangster and gangbuster in American history: Chicago bootlegger Al Capone and his famously incorruptible nemesis, Prohibition agent Eliot Ness.

Such comparisons have multiplied in recent days. Michael Avenatti, attorney for the adult-film star Stormy Daniels, recently drew what, for Trump’s opponents, is a tantalizing analogy: that just like Capone went down not for murder but tax evasion, Trump might be brought down by the relatively minor crime of campaign finance violations over the $130,000 his lawyer Michael Cohen reportedly paid to cover up Trump’s alleged affair with Daniels.

Avenatti’s analogy reflects a common misunderstanding of Capone. Yes, the gangster’s career ended following his 1931 conviction for income tax evasion. But this prosecution first required a sharp reversal in the way the government, the business community and the public tolerated — even celebrated — Capone in the years leading up to his trial. A similar seismic shift would be required today for the various investigations swirling around the president to make his impeachment a serious possibility.

For most of the 1920s, Americans accepted, ignored or applauded Capone’s rise to power and prominence as head of the Chicago Outfit, a criminal syndicate that stepped in to sate the city’s Prohibition-era thirst. That Capone broke the law to make his fortune — earning a reported $30 million in 1930 alone, or about $438 million in today’s dollars — was common knowledge. That he also would not hesitate to kill those who got in his way was no secret, either. After orchestrating the murder of one rival gangster in 1926, Capone called a news conference, lamenting the loss of his competitor to reporters he’d conveniently supplied with drinks.

Capone could flagrantly violate the law because of the close ties between his organization and Chicago’s public officials. Even before Prohibition, as the sociologist John Landesco noted in his 1929 study “Organized Crime in Chicago,” the Outfit had built relationships with police and politicos through running the city’s vice trade, brazenly corrupting local government officials to protect prostitutes from arrest.

When Prohibition unleashed a flood of cash into the Chicago underworld, Capone and his allies were well insulated from the authorities and more than rich enough to stay that way. Even the 1929 St. Valentine’s Day Massacre, in which the Outfit murdered seven rival gangsters and their associates, could not break this alliance between criminals and politicians, despite a growing public outcry.

How, then, did federal agents succeed in toppling the gangster just 2½ years after he got away with a massacre?

It wasn’t just taxes. By the mid-1920s, Chicago’s elite business executives soured on the notoriety produced by Capone and his associates. News coverage of these gangsters deeply damaged the city’s reputation, making it internationally infamous as a lawless and violent town. Investors and tourists grew reluctant to spend their money in America’s “Murder City,” while the labor racketeering schemes of Capone and other mobsters choked commerce even further.

Chicago’s business community pleaded for federal help in demolishing the alliance between local government and crime. But Washington remained aloof until the spring of 1930, when President Herbert Hoover — responding to the political risk posed by the Great Depression (not, as legend has it, the raucous parties at Capone’s Miami mansion that supposedly robbed him of sleep during a visit to Florida) — launched a concerted effort to nab Capone. Having made the preservation of Prohibition and the restoration of the rule of law centerpieces of his inaugural address, Hoover moved to make an example of the bootlegger whose fame flouted both promises.

This presidential order prompted the federal investigations led by Ness and Treasury agent Frank Wilson. These hit Capone on two fronts — economically, by raiding the breweries and distilleries that served as his primary income generators; and legally, by building tax evasion cases against the gangster and his associates. These investigations represented an existential threat to the Outfit, squeezing its profit margins even as the deepening Depression dried up the disposable income of its customers.

At the same time, public sentiment swung wildly against Capone. The vast wealth that made him an icon of the Roaring Twenties now seemed an unforgivable extravagance, while a nation exhausted by 10 years of Prohibition made the bootlegger the leading symbol of the dry law’s failures. Capone paved the way for his own destruction by openly courting celebrity, giving interviews to publications ranging from Liberty Magazine to Variety even while complaining about all the lies the media supposedly spread about him.

Chicago’s 1931 mayoral election also damaged the Outfit’s insulation as “Big Bill” Thompson, a longtime Capone ally, lost to Anton Cermak, a self-proclaimed reformer.

These cascading developments produced the final blow that toppled Capone. Members of his own organization — most famously the Mob lawyer E.J. O’Hare — turned on him, secretly informing on their boss to federal agents and ensuring his conviction in October 1931. Although popular myth has it that O’Hare — father of the war hero for whom Chicago’s airport is named — cooperated with the government to win his son a spot at the Naval Academy, investigators at the time recognized that the lawyer hoped to stop the ongoing federal assault on the Outfit (and protect himself from prosecution) by sacrificing his increasingly visible and erratic boss.

Capone’s dizzying decline from impregnable celebrity to federal prison occurred because his fame united the public, the government, the business community and his former allies against him. Only in such an environment did the tax evasion strategy succeed.

But Capone’s conviction wasn’t actually all that much of a victory for law and order. The Outfit would live on for decades, expanding its reach throughout the country even as it faded into the shadows. And with Capone behind bars, the various groups that had united to topple him largely lost interest in pursuing his less newsworthy successors. Although Ness remained in Chicago until 1933, working to dismantle the organization Capone left behind, he found himself increasingly isolated and unaided as Prohibition came to an end.

Like Ness and his Untouchables, special counsel Robert S. Mueller III’s investigative team has become burdened with the hopes of many Americans, who look to them with dreams of impeachment. But the actual story of Capone’s downfall shows that such an outcome is unlikely in our climate. That will change only if and when Trump’s outrageous rhetoric and erratic behavior — the threats of military conflicts and trade wars, the damage done to American credibility around the world — become an economic and electoral liability to those who enable him.

If that day comes, Democrats should not congratulate themselves prematurely. Trump’s rise, like Capone’s, is the result of fundamental flaws in American society and government that will not be solved by his departure from the Oval Office. His impeachment, like Capone’s conviction, would mean little if those underlying problems remain unaddressed.