WASHINGTON — On the day in June 2018 that President Trump declared he had the “absolute right” to pardon himself, Daniel S. Goldman met Representative Adam B. Schiff in a classic Washington way: They struck up a conversation in the green room at MSNBC.

The men, both Democrats, had plenty to talk about. Both former federal prosecutors, Mr. Schiff had a deep interest in Mr. Trump’s ties to Russia, while Mr. Goldman had investigated Russian organized crime. He told Mr. Schiff to call him if he could be of use. When Democrats won the House and Mr. Schiff became chairman of the House Intelligence Committee, he did, inviting Mr. Goldman to join his staff as the chief investigator.

Now Mr. Goldman is the lead author of a report, a draft of which committee members were able to review in private starting Monday evening, that forms the backbone of Democrats’ case for impeaching Mr. Trump. He is one of two unelected officials — the other is Stephen R. Castor, his Republican counterpart, who compiled the dissenting views — who have taken a crucial and unusually public job in the debate over the future of Mr. Trump’s presidency, and the nation.

The pair achieved a measure of Washington stardom over two weeks last month as they grilled witnesses during nationally televised public hearings. The House Judiciary Committee this week begins public hearings to consider articles of impeachment against Mr. Trump, meaning Mr. Goldman will probably take the spotlight again to present the Democrats’ case that the president abused his power by trying to enlist Ukraine to dig up damaging information on his political rivals, and it will fall to Mr. Castor to counter it.