Dale E. Ho ran the American Civil Liberties Union’s voting rights litigation department when President Trump’s first administration tried to put a citizenship question on the 2020 census.

The question, he said at the time, would “wreck the once-in-a-decade count of the nation’s population” by intimidating immigrants legal and not. In his first appearance before the Supreme Court, he argued against the plan, and the court blocked it. The administration eventually abandoned the effort.

Now, as a federal jurist in Manhattan, Judge Ho is facing the Trump administration from the other side of the bench. He is presiding over the criminal prosecution of Mayor Eric Adams and on Wednesday will hold a hearing on the government’s contentious motion to dismiss the charges against the mayor. The move set off mass resignations in the Justice Department.

From the moment Mr. Adams’s case was randomly handed to him in September, Judge Ho was thrust into a singular position: overseeing the first federal criminal prosecution of a sitting mayor of New York City — one who has recently allied himself closely with the president the judge once argued against in court.

Before joining the bench, he worked at the American Civil Liberties Union for about a decade.

David D. Cole, a law professor at Georgetown University, who worked closely with him at the organization, said Judge Ho was “diligent, careful, and unstinting in his pursuit of justice.”