Jerry Nadler and Donald Trump have a history. As Michael Daly has recounted in The Daily Beast, Trump approached Nadler in the 1980s, when Nadler was still a state assemblyman, and asked to build a skyscraper in his district. At 150 stories, it would have been the tallest building in the world, housing NBC’s new headquarters and some 5,700 apartments. Nadler said no. He wanted the city to use the site, which was on Manhattan’s Upper West Side, for a new affordable housing complex. Trump was furious. Not long after, he gave Nadler one of his typical derisive nicknames—“Fat Jerry.”

Trump, of course, did not know that three decades later, Nadler would be heading up a congressional committee with perhaps the most sweeping mandate—not to mention the clout and resources—to check his corrupt and inept administration. In March, as one of his first acts as chairman of the House Judiciary Committee, Nadler launched an expansive probe into Trump’s behavior as candidate and president. He has already sent more than 80 letters to individuals and entities, demanding documents that outline years of dealings with Trump. And in the days after Robert Mueller sent his report to the Department of Justice, Nadler made it clear that he would do everything in his power to ensure that his committee, the House, and ultimately the American people could see the full report and judge its implications and findings for themselves.

Nadler might seem like an unusual political leader to take on the role of presidential nemesis; he is thoughtful, thorough, and cerebral, a man of ideas—the opposite of Trump. But he knows the terrain better than most. He has sat on the Judiciary Committee for more than a quarter century, and spent most of that tenure on the subcommittee that oversees constitutional questions. He has watched Bill Clinton get impeached—and had a hand in not impeaching George W. Bush. But even for someone with Nadler’s wide range of experience, the House Judiciary Committee will be a tough battleground.

Because it deals with the most divisive issues, from abortion to gun rights to immigration to prison reform, Judiciary attracts the most conservative Republicans and the most liberal Democrats. The current Republican contingent is almost a rogues’ gallery of the more extreme Freedom Caucus bomb-throwers; Louie Gohmert, Jim Jordan, and Matt Gaetz are only the start. There are no thoughtful, moderate conservatives, as there were when Chairman Peter Rodino held hearings on the impeachment of Richard Nixon—no Tom Railsbacks, M. Caldwell Butlers, or William Cohens. The Democrats have some of their most liberal members on the committee, too, and some of their brightest stars—from Zoe Lofgren to Ted Deutch to Karen Bass and Caucus Chair Hakeem Jeffries, to Eric Swalwell, Ted Lieu, and Jamie Raskin. Nadler, however, stands out—not only for his keen legal mind, but because he understands the magnitude of what he is now required to do, and the man he is going up against.

Jerrold “Jerry” Nadler was born in Brooklyn, on June 13, 1947, almost a year to the day after Donald Trump, who was born, just one borough over, in Queens, on June 14, 1946. But while Trump’s family was wealthy, Nadler had a far more modest upbringing. His father, Emanuel, was an office manager for a gasoline distribution business. After Stuyvesant High, he went to Columbia on a Pulitzer scholarship, and to law school at night at Fordham while serving in the New York State Assembly. (They didn’t overlap, but Trump also spent time at Fordham before transferring to Wharton.) In 1992, after 16 years in the State Assembly, and two unsuccessful bids for higher office, the congressman representing Manhattan’s West Side, Ted Weiss, died days before the primary, and Nadler was chosen to replace him.

