James Comey’s appearance before the Senate Intelligence Committee on Thursday will be the most dramatic congressional testimony in decades.

Comey, who was fired as FBI director last month, could inflict real damage on President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE with his testimony — and for a few hours, he’ll have the nation’s full attention.

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Broadcast TV networks, as well as their cable counterparts, have cleared their schedules to provide wall-to-wall live coverage of the hearing, which is set to begin at 10 a.m. CNN has even started a countdown clock.

Comey has said it will be the only public testimony he will give on recent events, according to the chairman of the Senate Intelligence Committee, Richard Burr Richard Mauze BurrHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Bipartisan representatives demand answers on expired surveillance programs Rep. Mark Walker says he's been contacted about Liberty University vacancy MORE (R-N.C.).

The feverish atmosphere ahead of the former FBI director’s appearance is unlike anything seen in Washington in decades.

Jim Manley, who was a long-serving aide to former Senate Majority Leader Harry Reid Harry Mason ReidThe Supreme Court vacancy — yet another congressional food fight Trump seeks to turn around campaign with Supreme Court fight On The Trail: Battle over Ginsburg replacement threatens to break Senate MORE (D-Nev.), said he could not remember such public attention being paid to a congressional appearance since Anita Hill testified during Clarence Thomas’s confirmation hearing for the Supreme Court more than 25 years ago. Hill accused Thomas of sexual harassment; Thomas denied it and was confirmed.

Manley noted, however: “Things have radically changed since then, with the proliferation of cable TV as well as Twitter coverage and things like that. From a media perspective, this is going to be wildly different.”

There will also be an avid audience for any response that Trump offers to Comey. During Tuesday’s White House media briefing, press secretary Sean Spicer demurred when asked whether the president would watch the testimony. Spicer said only that Trump “has a full day on Thursday.”

Trump, meanwhile, said, “I wish him luck” when asked about Comey’s appearance.

The president is set to give a speech during the latter part of the Comey hearing, opening the possibility that he could be watching — and tweeting — in the opening hour.

Trump’s Twitter use has once again been the subject of controversy since the weekend. He has used the social media platform to criticize the mayor of London, his own Justice Department and the Gulf nation of Qatar.

Washington Post reporter Robert Costa tweeted on Tuesday that he had been “told by two WH sources that Pres. Trump does not plan to put down Twitter on Thursday. May live tweet if he feels the need to respond.”

The over-arching question on Thursday’s testimony is whether Comey will outline conduct on Trump’s part that comes close to obstruction of justice.

On Tuesday, ABC News reported — citing “a source familiar with Comey’s thinking” — that he would not make such an allegation himself.

But the source told the news organization that Comey “is not going to Congress to make accusations about the president’s intent, instead he’s there to share his concerns.”

Those concerns are believed to focus on two encounters with Trump. At a dinner on Jan. 27, Trump is alleged to have pressed Comey at least twice to pledge his “loyalty” to him. Comey is said to have responded only by promising his honesty. The White House disputes that account.

Comey is also believed to have kept a memo detailing a subsequent meeting with Trump on Feb. 14, the day after national security adviser Michael Flynn had been fired for giving misleading accounts of his communications with Russian Ambassador to the United States Sergey Kislyak.

On that occasion, Comey’s memo is said to outline how Trump asked him to drop the FBI investigation into Flynn’s links with Russia. The president reportedly told Comey, “I hope you can let this go” and described Flynn as a “good guy.”

Trump was asked at a news conference in mid-May whether he “at any time” urged Comey to “close or to back down” from the investigation.

“No. No. Next question,” he responded.

Yet another issue will be whether Comey will push back against Trump’s statement — made in the letter announcing his firing — that the FBI director had told the president on three occasions that he was not himself the target of federal investigation.

In the weeks since that letter was released, friends of Comey have suggested that statement from Trump is untrue.

Republicans are trying to walk a fine line as Comey’s testimony looms. They have displayed little appetite for a vigorous defense of the president — presumably because they are worried about the director delivering new bombshells.

At the same time, some in the party are questioning why the more damning details of Comey’s encounters with Trump have only come to light since his firing. While still in his position, Comey testified on Capitol Hill on May 3 and made no mention of any presidential effort to thwart his investigation.

Asked on that occasion by Sen. Mazie Hirono Mazie Keiko HironoManchin defends Supreme Court candidate Barrett: 'It's awful to bring in religion' Democrats shoot down talk of expanding Supreme Court Democrats unveil plan declaring racism a public health issue MORE (D-Hawaii) whether the attorney general or Department of Justice officials had ever acted to stop an FBI investigation, Comey replied: “Not in my experience. Because it would be a big deal to tell the FBI to stop doing something that — without an appropriate purpose.”

On Monday, the Republican National Committee’s rapid response unit sent reporters an email detailing a number of interviews and comments in which this point was raised.

Republican strategist Ford O’Connell suggested Democrats could be overestimating the effects of Comey’s testimony.

“There is only one question that matters for the president, and that is, ‘Is James Comey going to say he obstructed justice?’ ” he said. “According to ABC News, he is not going to do that.”

But with all eyes in Washington on the hearing on Thursday, the stakes could hardly be higher.

The Memo is a reported column by Niall Stanage, primarily focused on Donald Trump’s presidency.