On July 26, 2016, after WikiLeaks disseminated the D.N.C. e-mails, Steele filed yet another memo, this time claiming that the Kremlin was “behind” the hacking, which was part of a Russian cyber war against Hillary Clinton’s campaign. Many of the details seemed far-fetched: Steele’s sources claimed that the digital attack involved agents “within the Democratic Party structure itself,” as well as Russian émigrés in the U.S. and “associated offensive cyber operators.”

Neither of these claims has been substantiated, and it’s hard to imagine that they will be. But one of the dossier’s other seemingly outlandish assertions—that the hack involved “state-sponsored cyber operatives working in Russia”—has been buttressed. According to Special Counsel Mueller’s recent indictment of thirteen Russian nationals, Kremlin-backed operatives, hiding behind fake and stolen identities, posed as Americans on Facebook and Twitter, spreading lies and fanning ethnic and religious hatred with the aim of damaging Clinton and helping Trump. The Kremlin apparently spent about a million dollars a month to fund Internet trolls working round-the-clock shifts in a run-down office building in St. Petersburg. Their tactics were similar to those outlined in Steele’s Charlemagne investigation, including spreading falsehoods designed to turn voters toward extremism. The Russian operation also involved political activism inside the U.S., including the organizing of bogus pro-Trump rallies.

In England, Steele kept cranking out memos, but he was growing anxious about the lack of response from the F.B.I. As the summer wore on, he confided in an American friend, Jonathan Winer, a Democratic lawyer and foreign-policy specialist who was working at the State Department. Steele told him that Orbis sources had come across unsettling information about Trump’s ties to Russia. Winer recalls Steele saying that he “was more certain of it than about any information he’d gotten before in his life.” Winer told me, “Chris was deeply disturbed that the Kremlin was infecting our country. By hacking our computers and using WikiLeaks to disseminate the information—it was an infection. He thought it would have really bad consequences for the U.S. and the U.K., for starters. He thought it would destabilize these countries. He wanted the U.S. government to know. He’s a very institution-oriented person.”

During the previous two years, Steele had been sending Winer informal reports, gratis, about raw intelligence that he’d picked up on Ukraine and related areas while working for commercial clients. Winer, who encouraged Steele to keep sending the reports, estimated that he had received more than a hundred and twenty of them by 2016. He and others at the State Department found the research full of insights. Winer recalls Victoria Nuland, the top official overseeing U.S. policy on Russia, expressing surprise at how timely Steele’s reports were. A former top State Department official who read them said, “We found the reports about eighty per cent consistent with other sources we had. Occasionally, his sources appeared to exaggerate their knowledge or influence. But Steele also highlighted some players and back channels between Russia and Ukraine who became important later. So the reports had value.”

In September, 2016, Steele briefed Winer on the dossier at a Washington hotel. Winer prepared a two-page summary and shared it with a few senior State Department officials. Among them were Nuland and Jon Finer, the director of policy planning and the chief of staff to Secretary of State John Kerry. For several days, Finer weighed whether or not to burden Kerry with the information. He’d found the summary highly disturbing, but he didn’t know how to assess its claims. Eventually, he decided that, since others knew, his boss should know, too.

When Kerry was briefed, though, he didn’t think there was any action that he could take. He asked if F.B.I. agents knew about the dossier, and, after being assured that they did, that was apparently the end of it. Finer agreed with Kerry’s assessment, and put the summary in his safe, and never took it out again. Nuland’s reaction was much the same. She told Winer to tell Steele to take his dossier to the F.B.I. The so-called Deep State, it seems, hardly jumped into action against Trump.

“No one wanted to touch it,” Winer said. Obama Administration officials were mindful of the Hatch Act, which forbids government employees to use their positions to influence political elections. The State Department officials didn’t know who was funding Steele’s research, but they could see how politically explosive it was. So they backed away.

Steele believed that the Russians were engaged in the biggest electoral crime in U.S. history, and wondered why the F.B.I. and the State Department didn’t seem to be taking the threat seriously. Likening it to the attack on Pearl Harbor, he felt that President Obama needed to make a speech to alert the country. He also thought that Obama should privately warn Putin that unless he stopped meddling the U.S. would retaliate with a cyberattack so devastating it would shut Russia down.

Steele wasn’t aware that by August, 2016, a similar debate was taking place inside the Obama White House and the U.S. intelligence agencies. According to an article by the Washington Post, that month the C.I.A. sent what the paper described as “an intelligence bombshell” to President Obama, warning him that Putin was directly involved in a Russian cyber campaign aimed at disrupting the Presidential election—and helping Trump win. Robert Hannigan, then the head of the U.K.’s intelligence service the G.C.H.Q., had recently flown to Washington and briefed the C.I.A.’s director, John Brennan, on a stream of illicit communications between Trump’s team and Moscow that had been intercepted. (The content of these intercepts has not become public.) But, as the Post noted, the C.I.A.’s assessment that the Russians were interfering specifically to boost Trump was not yet accepted by other intelligence agencies, and it wasn’t until days before the Inauguration that major U.S. intelligence agencies had unanimously endorsed this view.

In the meantime, the White House was unsure how to respond. Earlier this year, at the Council on Foreign Relations, former Vice-President Joe Biden revealed that, after Presidential daily briefings, he and Obama “would sit there” and ask each other, “What the hell are we going to do?” The U.S. eventually sent a series of stern messages to the Russians, the most pointed of which took place when Obama pulled Putin aside on September 5th, at a G20 summit in China, and reportedly warned him, “Better stop, or else.”

But Obama and his top advisers did not want to take any action against Russia that might provoke a cyber war. And because it was so close to the election, they were wary about doing anything that could be construed as a ploy to help Clinton. All along, Trump had dismissed talk of Russian interference as a hoax, claiming that no one really knew who had hacked the D.N.C.: it could have been China, he said, or a guy from New Jersey, or “somebody sitting on their bed that weighs four hundred pounds.” Trump had also warned his supporters that the election would be rigged against him, and Obama and his top aides were loath to further undermine the public’s faith.

In early September, 2016, Obama tried to get congressional leaders to issue a bipartisan statement condemning Russia’s meddling in the election. He reasoned that if both parties signed on the statement couldn’t be attacked as political. The intelligence community had recently informed the Gang of Eight—the leaders of both parties and the ranking representatives on the Senate and House Intelligence Committees—that Russia was acting on behalf of Trump. But one Gang of Eight member, Senate Majority Leader Mitch McConnell, expressed skepticism about the Russians’ role, and refused to sign a bipartisan statement condemning Russia. After that, Obama, instead of issuing a statement himself, said nothing.

Steele anxiously asked his American counterparts what else could be done to alert the country. One option was to go to the press. Simpson wasn’t all that worried, though. As he recalled in his subsequent congressional testimony, “We were operating under the assumption at that time that Hillary Clinton was going to win the election, and so there was no urgency to it.”

Contemporaneous F.B.I. text messages disclosed recently by the Wall Street Journal reflect a similar complacency. In August, 2016, two F.B.I. employees, Lisa Page and Peter Strzok, texted about investigating possible collusion between Trump and the Russians. “omg I cannot believe we are seriously looking at these allegations and the pervasive connections,” Strzok wrote. Page suggested that they could take their time, because there was little reason to worry that Clinton would lose. But Strzok disagreed, warning that they should push ahead, anyway, as “an insurance policy” in case Trump was elected—like “the unlikely event you die before you’re 40.”

When excerpts of these texts first became public, Trump defenders such as Trey Gowdy seized on them as proof that the F.B.I. had schemed to devise “an insurance policy” to keep Trump from getting elected. But a reading of the full text chain makes it clear that the agents were discussing whether or not they needed to focus urgently on investigating collusion.

In late summer, Fusion set up a series of meetings, at the Tabard Inn, in Washington, between Steele and a handful of national-security reporters. These encounters were surely sanctioned in some way by Fusion’s client, the Clinton campaign. The sessions were off the record, but because Steele has since disclosed having participated in them I can confirm that I attended one of them. Despite Steele’s generally cool manner, he seemed distraught about the Russians’ role in the election. He did not distribute his dossier, provided no documentary evidence, and was so careful about guarding his sources that there was virtually no way to follow up. At the time, neither The New Yorker nor any other news organization ran a story about the allegations.

Inevitably, though, word of the dossier began to spread through Washington. A former State Department official recalls a social gathering where he danced around the subject with the British Ambassador, Sir Kim Darroch. After exchanging cryptic hints, to make sure that they were both in the know, he asked the Ambassador, “Is this guy Steele legit?” The Ambassador replied, “Absolutely.” Brennan, then the C.I.A. director, also heard the rumors. (Nunes reportedly plans to examine Steele’s interactions with the C.I.A. and the State Department next.) But Brennan said recently, on “Meet the Press,” that he heard just “snippets” about the dossier “in press circles,” emphasizing that he didn’t see the dossier until well after the election, and said that “it did not play any role whatsoever” in the intelligence community’s appraisal of Russian election meddling. Brennan said of the dossier, “It was up to the F.B.I. to see whether or not they could verify any of it.”

It wasn’t until October 7, 2016, that anyone in the Obama Administration spoke publicly about Russia’s interference. James Clapper, Obama’s director of National Intelligence, and Jeh Johnson, the head of the Department of Homeland Security, issued a joint statement saying that the U.S. intelligence community was “confident” that Russia had directed the hacking of the Democratic National Committee’s e-mails. James Comey, then the F.B.I. director, had reportedly changed his mind about issuing a public statement, deciding that it was too close to the election to make such a politically charged assertion.

In a normal political climate, the U.S. government’s announcement that a foreign power had attacked one of the two dominant parties in the midst of a Presidential election would have received enormous attention. But it was almost instantly buried by two other shocking news events. Thirty minutes after the statement was released, the Washington Post brought to light the “Access Hollywood” tape, in which Trump describes how his celebrity status had allowed him to “grab” women “by the pussy.” A few hours after that, WikiLeaks, evidently in an effort to bail out Trump by changing the subject, started posting the private e-mails of John Podesta, Clinton’s campaign chairman. The intelligence community’s assessment was barely noticed.