When sorrows come, Shakespeare observed, they come not single spies, but in battalions. The same goes for former US president Donald Trump’s legal troubles.

The latest trouble for Trump strikes at the heart of his identity as a wealthy businessman who wrote the bestselling book The Art of the Deal. On Tuesday his company was convicted of a 15-year criminal scheme to defraud tax authorities.

“Add tax fraud to the long list of Trump’s accomplishments,” tweeted Adam Schiff, chairman of the House of Representatives’ intelligence committee.

The case centered on charges that the Trump Organization, which operates hotels, golf courses and other assets around the world, paid personal expenses like rent and car leases for top executives without reporting the income, and paid them bonuses as if they were independent contractors.

Trump himself was not charged but prosecutors alleged that he “knew exactly what was going on”. During his closing argument, prosecutor Joshua Steinglass showed jurors a lease Trump signed for a company-paid apartment and a memo Trump initialed authorising a pay cut for another executive who got perks.

“Mr Trump is explicitly sanctioning tax fraud,” Steinglass argued.

In a normal political universe, such a revelation would sink Trump’s hopes of a White House comeback in 2024. But given that he once boasted he could shoot someone in the middle of New York’s Fifth Avenue and not lose any votes, explicitly sanctioning tax fraud might not quite cut it.

Indeed, as comedian Dave Chappelle noted in a recent Saturday Night Live monologue, Trump has turned his ability to bend and break rules into a political virtue. “He said, ‘I know the system is rigged because I use it.’” When Hillary Clinton accused him of not paying taxes, Trump retorted: “That makes me smart.”

In Chappelle’s view, this rare willingness to expose what goes on behind the doors of the rich man’s club endeared Trump to working-class voters in 2016. The implication is that you would do it too, if you could, so good on him.

But six years later, the political landscape is different and the act is looking tired to many, even – increasingly – in his own party. No previous former US president, and no previous presidential candidate, has faced such a mountain of allegations and investigations.

The Trump Organization also separately faces a fraud lawsuit brought by New York state attorney general Letitia James. She wrote on Twitter on Tuesday: “Today’s guilty verdict against the Trump Organization shows that we will hold individuals and organizations accountable when they violate our laws to line their pockets.”

Trump himself is being investigated by the justice department over his handling of sensitive government documents after he left office in January 2021 and his attempts to overturn the November 2020 election, which he lost to Joe Biden.

A prosecutor in Georgia is scrutinising Trump and his allies over an attempt to subvert democracy in that state. Last month the US supreme court cleared the way for the handover of the former president’s tax returns to a congressional committee.

In the attrition of legal trench warfare, these cases may be gradually wearing down Trump’s political resilience, especially combined with three successive elections that suggest he is more of a loser than a winner.

His winning argument in 2016 was that, having cultivated the image of a successful businessman on his reality TV show The Apprentice, he could now bring the same acumen to governing the country. And in a sense, he did: with fraud, deceit and contempt for the rule of law.