Michael Cohen’s testimony will likely provide a window into Trump’s business practices. But there remains much more to uncover. Photograph by Mark Peterson / Redux for The New Yorker

Michael Cohen is a bad man. He was a bad man before he met Donald Trump, he remained a bad man afterward, and he became, if anything, even worse after Trump started running for President. Michael Cohen has—it seems possible—become penitent and regretful about one aspect of his badness, specifically the bad things that he did for Trump over the past twelve years. Yet he has remained defiantly silent on the many, many other bad things he has done. When he leaves prison (he is scheduled to start a three-year sentence in May), he will remain a very rich man, wealthy from a decade of grifting.

On Wednesday, Cohen will try to be a hero of this age, in the Greek sense of the hero: a flawed man with special powers, brought low by his own hubris, who moves the plot forward. It could be his greatest act of heroism. During his testimony, he will—he claims—lay bare many things that he knows about Trump, and he will bring proof. He will bring receipts that show that Trump knowingly reimbursed Cohen for his contribution to an illegal scheme to silence a woman with whom Trump had an affair. He will tell us, in detail, Trump’s view of America, the Presidency, African-Americans, and how, Cohen says, Trump said that running for President was the “greatest infomercial in political history.” Most important, perhaps, Cohen will provide something that followers of the special counsel’s investigation have desperately wanted: actual financial statements from 2011 to 2013, a period when the Trump Organization was engaged in a range of suspicious business practices around the world.

Republicans are already seeking to impeach Cohen’s testimony, to reveal him to be a liar and a criminal. That will be easy to do. Cohen went to one of the worst law schools in America, and then spent years working alongside a string of lawyers and others who would go on to be convicted of crimes. His first legal job was with a lawyer who later pleaded guilty to bribing insurance adjusters. Later, Cohen worked with a doctor convicted of insurance fraud. Cohen also worked closely with taxicab moguls, including his father-in-law, who would be convicted of crimes. Cohen himself remained unindicted. (His life story is told beautifully in an episode of the podcast “Trump, Inc.”) And Cohen, surely, has lied constantly, including before the very committee that hosts him today. Before his flip away from Trump, Cohen was a voluble but duplicitous source for countless reporters, who knew that Cohen would always answer his phone and would always talk (and always lie). But his mendacity was so obvious and easily proved that the falsehoods acted, often, as confirmations. And he is, of course, a convicted felon going to prison. If the Republicans are wise—though they likely won’t be—they could use some restraint, and let Cohen impeach himself.

Yet Cohen’s testimony is a defining moment, even if we dismiss every unverified claim—his accounts of overhearing, from Trump, racist comments and a con man’s disdain for his country—and consider only the documentary evidence. Most telling of all, perhaps, is the fact that Cohen—this scheming, awful man—is the person the President retained as his private lawyer until just last year. This is the company the President keeps; this is who he is.

There is a final fact about Cohen that should also be kept in mind. Cohen was not a singular figure in the Trump Organization. He doesn’t bring all the goods. According to his publicly filed records, Trump has more than five hundred separate lines of business, and Cohen, it seems, was involved in only a handful of them. His testimony on Wednesday should not be thought of as the full accounting of the inner workings of Trump’s world. Much of what Cohen has to say he learned by overhearing a conversation or taking note of a brief aside. He apparently has financial records from 2011 through 2013, but doesn’t, it appears, have documents from any other year. (This is because Cohen played a role in an application for a loan from Deutsche Bank.) He wasn’t a central player in the business with access to all the documentation. The true insiders—Allen Weisselberg, Jason Greenblatt, George Sorial, and the older Trump children—know far more about every aspect of the Trump business than Cohen does.

Wednesday’s testimony is a huge moment in Trump’s Presidency. It is unlikely, though, to diminish the country’s political chasm. Cohen will be dismissed by the President and his allies as a liar trying to reduce his prison sentence. Trump’s supporters will continue to back him. But it will be a kind of accounting, under oath and before the world, from Cohen that we haven’t had yet. It is only a beginning, a timid beginning, that both gives new information and is also a crucial performance, a visual image of Trump’s indecency that will be remembered for generations. It is unlikely to be the last.