WASHINGTON — On the 140th day of the Trump presidency — one for each allotted character on the executive Twitter feed that stayed conspicuously silent all Thursday morning — a very tall man with a very strange place in this very bewildering moment in American history strolled into Hart Senate Office Building 216, shot a quick glance at the masses arrayed behind him and presented a seen-it-all city with something unusual.
In a capital accustomed to overcooked spectacle and insufferable congressional testimony, James B. Comey delivered on the hype.
For about two and a half hours, the room fell into an anxious hush, punctured sporadically by audible emissions of surprise at the remarks of a deposed F.B.I. director with a collection of Trump-branded knives in his reputational torso.
Senators settled into their telegenic gazes, steely but approachable, often whispering to one another as the witness held forth.
Photographers clicked with impunity, descending on every twitch: a wave of the hand, a cock of the head, a woman delivering glasses of ice water to Mr. Comey’s table before he arrived.
And the headliner summoned a theatrical swagger to match the moment, assuming a role with little precedent: a dispatched federal employee — hero, villain, Shakespearean character in the 2016 election and early Trump administration — staring into the cameras and talking to the president who had fired him.
“I’ve seen the tweet about tapes,” he said in one flourish, referring to a Twitter post in which President Trump suggested that he had recorded his interactions with Mr. Comey. “Lordy, I hope there are tapes.”
So much about the Trump era has scrambled Washington’s sense of itself, as promised. In the haze, it can be difficult to tease out which baffling elements arrived with this president and which were pre-existing conditions, already endemic to an industry town with a Trumpian self-obsession long before he moved in.
Inside the room on Thursday, these dual forces seemed to hurtle into each other, fusing in real time. Echoes of scandals past — Iran-contra, Anita Hill, Monica Lewinsky — wafted overhead, visiting the memories of Senate veterans.
But something was different. The zingers ricocheted instantly across the web. Reporters kept an eye on Twitter, awaiting a presidential response that did not arrive as Mr. Comey spoke. (Mr. Trump’s son Donald Jr. did weigh in.)
A modest walk away, the proceedings were aired above the bar at the Trump International Hotel.
At the Capitol, attendees took stock of the ubiquity, and wondered. A Trump supporter, Patrick Wells, 49, who had traveled from Massachusetts to support the president, marveled that the hearing had knocked “The Price Is Right” from its broadcast perch. “They usually only do that if it’s an assassination or a terrorist attack,” he said.
Mr. Wells eyed the slithering line for public admission warily before resigning himself to an overflow room.
Even the lawmakers seemed taken by the spectacle.
“West Virginia is very interested in this hearing that we’re having today,” the state’s Democratic senator, Joe Manchin III, said dryly at one point.
West Virginia had company.
Restaurants opened early for the main event, with Russian vodka specials on offer. Taxis swore off smooth jazz and Top 40 for audio feeds from the Senate Intelligence Committee.
Off camera, wandering senators, often loath to endure full hearings for even their own committees, slipped into the room to watch their colleagues work.
For much of the morning, boldfaced names dotted the crowd, at least by Capitol standards, spawning the sort of dialogue that might translate poorly in most corners of the country.
Who was that woman snapping all the cellphone photos? (It was Greta Van Susteren of MSNBC.)
Isn’t that the congressman who resigned in disgrace a few years ago? (Yes, it was former Representative David Wu, Democrat of Oregon, who had scored a seat inside.)
Get a look at Preet Bharara, the also-axed former United States attorney for Manhattan. (He sat a few feet behind Mr. Comey, live-tweeting in support of his comrade-in-job-loss.)
Mostly, though, attention rarely strayed from the witness chair, where Mr. Comey held his audience with an uncommon skill set for a veteran law enforcement official: a novelist’s instinct for narrative and, occasionally, levity.
He likened reporters to sea gulls on the beach. He used “fuzz” as a hard-to-track metaphor and quoted England’s Henry II.
He defended his credentials as a reader of people with: “I’ve had a lot of conversations with humans over the years.”
And he appeared inclined to win support among viewers, inside the building and out, with an implicit contrast in style to Mr. Trump, reaching often for notes of humility.
“Slightly cowardly,” he said of his own behavior in one interaction with Mr. Trump.
“I don’t want to make you sound like I’m Captain Courageous,” he mustered later.
When Senator Kamala Harris, Democrat of California, thanked him for coming, Mr. Comey reminded her that his employment status had opened up his calendar. “I’m between opportunities now,” he said.
Others on hand arrived without a formal invitation.
Joe Noser, 19, had camped out overnight at the Capitol to secure a prime spot in line. He invoked the Lewinsky affair from the late 1990s, the period of his birth.
“It’s not a sex scandal but it’s still important,” he said of Thursday’s events. “It will be the coolest thing to tell your grandkids down the road: ‘I was able to see the Comey hearing.’”
Nearby, Victoria Herring, 20, who also stayed at the Capitol on Wednesday night to reach the room before dawn, waited among the congressional pilgrims.
The line stretched down hallways and around corners. Most people would never even sniff the room. Perhaps, Ms. Herring suggested, Mr. Trump would appreciate the scene.
“He loves drama,” she said.
And he loves a show with big ratings, or used to.