Or maybe Comey's first public outing since President Donald Trump sacked him on May 9 will just be a damp squib.

The questions that will be put to Comey have been canvassed in detail:

??? Did he believe that Trump was pressuring him to back off from aspects of the investigation of the Trump campaign's ties to Russia?

??? What was the detail of his conversations with Trump?

??? And yes, please, the senators will want the memos Comey reportedly wrote after several encounters with the President.

??? Did Comey feel that Trump was obstructing justice?

??? Did Trump demand Comey's personal loyalty?

??? Had Comey, as claimed by Trump, informed the President no less than three times that Trump, personally, was not under investigation?

But here's the thing - Comey has been tic-tacking with Robert Mueller on what he can and can't say and, reportedly, they have arrived at a game plan.

Mueller was dramatically appointed as special counsel to investigate what Trump dismisses as "this Russia thing", on the heels of Comey's dramatic sacking.

The most powerful man without a job in Washington, Comey is a hive of contradictions: a Democrat turned Republican; a Catholic turned Evangelical turned Methodist; he's been described as one who postures as apolitical, but who also enjoys the limelight.

He's described variously as quixotic; as supremely confident and fiercely independent, by admirers; as equipped with "media savvy arrogance", by detractors; the possessor of "stubbornness, ego, and some self-righteousness at work".

Trump and Republicans cheered Comey on and Democrats railed against him for the damage they saw inflicted on Hillary Clinton's campaign by Comey's handling of the investigation into her email server in the last days of the 2016 election campaign.

But now, Democrats are rallying to Comey, as the President denounces him as "a nut job", and Trump supporters are running TV advertisements to discredit him.

After Trump's request that he pull back on the Russia investigation, Comey was so worried he confronted Attorney-General and Trump loyalist Jeff Sessions, demanding that he not be left alone again with Trump, The New York Times reported on Tuesday.

Earlier reports said that, before making his controversial request, Trump had ordered all other officials to leave the Oval Office.

Comey stopped Americans in their tracks in March, when he revealed for the first time that the FBI had been investigating possible collusion between Moscow and the Trump campaign since July 2016.

"I have been authorised by the Department of Justice to confirm that the FBI, as part of our counterintelligence mission, is investigating the Russian government's efforts to interfere in the 2016 presidential election," he told a hearing of the House Intelligence Committee.

"That includes investigating the nature of any links between individuals associated with the Trump campaign and the Russian government, and whether there was any co-ordination between the campaign and Russian efforts."

The hearing before the Senate Intelligence Committee is fraught with risk for Trump, who has repeatedly denied any wrongdoing.

Comey is on the witness stand. But depending on what he says, Trump, some of his closest aides - think son-in-law Jared Kushner and sacked National Security Adviser Michael Flynn; and a slew of campaign associates could land in the dock.

"Clearly, it would be very, very troubling if the President of the United States is interfering in investigations that affect potentially the President and his closest associates," Virginia Senator Mark Warner, the top Democrat on the Senate intelligence committee, said on Sunday.

"We've known since Watergate rules of the road that [a] president shouldn't intervene in an ongoing investigation. It would be unthinkable if the President actually did what was reported."

Warner conceded that, while the committee's investigation had turned up "a lot of smoke", there still was "no smoking gun".

The "smoke" alluded to by Warner is a swirl of news reports, many based on intelligence leaks, on numerous meetings between Trump aides and Russian officials; evidence of efforts to conceal those meetings; and, as reported by Yahoo last week, of moves in the first days of the administration to make a priority of lifting sanctions on Russia - which was beaten back by the State Department.

Trump has done nothing to endear himself to Comey. Quite the reverse - the White House has denounced him as unfit to run the FBI. And apart from that "nut job" line, which Trump used in explaining to Russian Foreign Minister Sergei Lavrov that sacking Comey had eased the pressure on him, the President has also rubbished Comey as a "showboat".

Having so thoroughly dissed Comey, Trump awaits Thursday's hearing in the knowledge that he has no leverage over the former FBI director. And when it comes to credibility and truth telling, Comey has the high ground - Trump doesn't.

Comey has nothing to lose; Trump does - bigly. If Comey contradicts Trump's denials and, if there is evidence to support him, Trump could conceivably face charges of attempting to obstruct justice.

It's being likened to a cross between the Bourne movies and House of Cards. For excitable Democrats, this is the beginning of the end for Trump; for many Republicans, it's just lies built on innuendo and guilt-by-association - and, they insist, after months of investigation, there still is no proof that Trump or his campaign colluded with the Russians.

And for Donald Trump it's just a witch-hunt. But in some quarters, the wildness as Trump has been lashing out on Twitter this week, is read as proof that he's a very worried man.