After two years of near absolute silence, Robert S. Mueller III, the special counsel, is testifying on Wednesday before lawmakers on the House Judiciary and the House Intelligence Committees. For the lawmakers, it’s an opportunity to publicly grill Mr. Mueller on the report he produced this year and the investigation itself.

Here are the lawmakers to watch during the televised back-and-forth.

The House Judiciary Committee

The leadership: Representatives Jerrold Nadler of New York and Doug Collins of Georgia

Both Representatives Jerrold Nadler, the New York liberal who leads the committee, and Doug Collins of Georgia, the committee’s top Republican, set the tone for the hearing with opening statements outlining their party’s respective arguments. Mr. Nadler was a key force in negotiating Mr. Mueller’s testimony. Mr. Collins began by emphasizing that the investigation was over and that President Trump was innocent.

In his questioning, Mr. Nadler achieved what Democrats wanted from the hearing: Mr. Mueller said aloud that the report did not say that there was no collusion — “not a legal term,” Mr. Mueller said in his opening remarks — and agreed that the report did not exonerate the president.

Mr. Collins, for his part, hammered Mr. Mueller on whether “collusion,” Mr. Trump’s preferred phrase and “conspiracy,” the term used in the report, meant the same thing. Mr. Mueller said they were not synonymous.