It was the testimony of a once-obscure former law enforcement official. Before the Senate Select Committee on Intelligence. At 10 in the morning. On a workday.

Not your usual ratings gold.

No matter. Roughly 19.5 million Americans tuned in on Thursday to watch James B. Comey, the former F.B.I. director, unspool the tale of his awkward, unsettling and, at times, ethically questionable encounters with President Trump.

That is about the same number of people who watched Game 2 of this week’s N.B.A. finals between the Golden State Warriors and the Cleveland Cavaliers.

Mr. Comey’s full audience was undoubtedly even bigger. The viewership figure released on Friday by the television tracking firm Nielsen did not include statistics for PBS, C-Span or the Fox broadcasting affiliates that carried the hearing live.