James Comey was the acting attorney general of the United States in March 2004 when two emissaries from the Bush White House marched to the hospital bed of the attorney general, John Ashcroft, and asked him to renew the warrantless mass surveillance programme code-named Stellar Wind – a programme whose legality had been questioned by the Office of Legal Counsel. Comey, who is six foot eight, stood between the White House flunkies and the sick man’s bed, and they retreated. Soon after, he informed Bush that if the secret programme were reauthorised over the objections he had seen, he himself and the head of the FBI, Robert Mueller, would lead a mass resignation from the justice department. Bush fell back; and a chink opened in the system whose vastness and illegality would eventually be exposed by Edward Snowden. It was one of very few moments in the Bush-Obama years that bore the stamp of civic courage: someone inside government had been willing to sacrifice his career to uphold the constitution. So when, in September 2013, President Obama appointed Comey as the next director of the FBI, the move was generally applauded.

Last summer, Comey lost the support of Democrats by his investigation of Hillary Clinton’s use of a private email server for receiving classified documents. He brought no indictment against Clinton and said no responsible prosecutor would have done so, but described her actions as careless and irresponsible. In a hearing in early July by the House Committee on Oversight and Government Reform, Republican congressmen said that they were baffled by Comey’s refusal to indict; and for their benefit, he repeated both parts of his characterisation: Clinton’s abuse did not warrant prosecution, because no crime had been committed, but the risk to national security with her at-home server had been real and blamable. The chair of the committee, Jason Chaffetz, extracted a promise that Comey would notify them if new evidence developed. On 28 October, he sent a short letter to the committee: new emails, possibly relevant, had turned up and were being investigated. On 6 November, two days before the election, he announced that the emails turned out to contain nothing of interest.

Democrats had said all along that Comey should never have issued the obiter dicta on Clinton’s conduct. After she lost the election by the narrowest of margins in four states, many Democrats held Comey answerable for the defeat. He replied in a more recent congressional hearing, on 3 May before the Senate Judiciary Committee, that the very thought that his letter might have affected the November result made him ‘mildly nauseous’. According to a story in the Washington Examiner, this was the remark that precipitated his firing on 9 May:

‘Trump is notoriously thin-skinned,’ said a Trump insider. ‘He probably took it the wrong way and probably thought it was directed at him,’ added the source.

The explanation is strangely credible, in view of everything that is known about Trump as president, his modus operandi and his manner of arriving at weighty decisions.

Before this, the latest alarm had occurred on 20 March, when Comey confirmed that he was overseeing an FBI investigation into Russian interference in the election and possible collusion by the Trump campaign. The truth is, if Comey has occasionally stepped beyond the proper function of a prosecutor, he has shown great impartiality of attack. He relieved the attorney general, Loretta Lynch, as the public voice of the Clinton investigation, only after Lynch was compromised by the publicity around a drawn-out private conversation with Bill Clinton. Lynch owed him her appointment as US attorney; it later emerged she had instructed Comey never to call the FBI work on Hillary an ‘investigation’: he was to refer to it as ‘the matter’. A certain loss of trust, then, between Comey and Lynch, and the faltering self-confidence of Lynch herself, together account for a good deal of his conduct last summer.

His October letter to the oversight committee came out of a different sort of underbrush. He had promised to let them hear of any developments – a promise he should have refused. Regarding a search-in-progress, every prosecutor is instructed to preserve a conscientious silence. There was an additional complexity, however, owing to his two distinct continuing roles: first as an investigator of the Clinton Foundation – in July, he told the committee that the investigation was still active – and second as an FBI director under the eye of hostile lawmakers who were themselves in touch with FBI agents.

In an extraordinary Daily Beast story last November, Wayne Barrett disclosed the extensive contacts between the former New York mayor and recent Trump adviser Rudy Giuliani, the retired right-wing FBI official James Kallstrom, and a network of discontented active agents. From these sources emanated hints of a coming ‘further investigation’ of Hillary Clinton. There was, or so right-wing radio hosts were reporting, a civil war within the FBI, and one thing probably driving Comey’s October letter was the threat of more leaks from inside the agency. By then, he would have known enough about Clinton and Trump to knock the bottom out of the lowest measurable public opinion of either candidate; but like the rest of the country, he assumed that Clinton would win. Barrett said in a post-election interview that he believed the 168-hour scandal the mainstream press had made of Comey’s matter-of-fact letter did more damage than the letter itself.

With the Trump presidency, a clear pattern has emerged in one respect at least. Money is the large and always prevalent motive. Power is taken chiefly as a means to secure the possession of money, and to open new channels for its acquisition. Trump is not a political character at all; his actions are aimed rather at protecting corruption and compelling loyalty. Russians have been mentioned, in the liberal press, more often than the existing evidence justifies, but a connection may exist between Trump’s American oligarchs and the Russian oligarchs, a connection either partly known or guessed at by Trump himself. Those words from Comey that could seem to speak of a nauseated detachment from the president, along with his words about the FBI investigation of possible collusion, would have been enough to tip the scale towards the latest dismissal. In the same way, a few weeks earlier, Trump fired the US attorney for the Southern District of New York, Preet Bharara, after assuring him that his position was secure. The two cases have this in common, that the sacked official was a prosecutor who would have known unsavoury things about Trump, and would be in a position to learn more.

Meanwhile, the newly confirmed deputy attorney general, Rod J. Rosenstein, who wrote the memorandum on which Trump claimed to have based his decision, took pains to let readers know the initiative came from Trump: ‘As you and I have discussed …’ Trump in his letter firing Comey sought to bind the departing director to another promise: ‘While I greatly appreciate your informing me, on three separate occasions, that I am not under investigation …’

Nobody knows what will follow. There have been calls for a special prosecutor, and evocations of the Saturday Night Massacre when Nixon found a justice official to fire his own appointed special prosecutor. The decision reached Comey when it flashed on a TV screen while he was addressing FBI agents in Los Angeles; he took it initially as a joke, but afterwards the helicopter cameras of Fox News followed his motorcade to the airport the way they followed O.J. Simpson’s white Bronco in 1994. Three comments on Twitter go some way to capture the wildness of the moment. From Donald Trump: ‘Comey lost the confidence of almost everyone in Washington, Republican and Democrat alike. When things calm down, they will be thanking me!’ From Edward Snowden: ‘This FBI Director has sought for years to jail me on account of my political activities. If I can oppose his firing, so can you.’ From Preet Bharara: ‘Here's the @MerriamWebster definition of “pretext”.’