WASHINGTON — President Trump and his allies spent months promising that a report on the origins of the F.B.I.’s Russia investigation would be a kind of Rosetta Stone for Trump-era conspiracy enthusiasts — the key to unlocking the secrets of a government plot to keep Mr. Trump from being elected in 2016.
On that point, the report by the Justice Department’s inspector general, Michael E. Horowitz, did not deliver, even as it found serious problems with how F.B.I. officials justified the surveillance of a Trump campaign aide to a federal court.
But by the time it was released, the president, his attorney general, his supporters in Congress and the conservative news media had already declared victory and decamped for the next battle in the wider war to convince Americans of the enemies at home and abroad arrayed against the Trump presidency.
They followed a script they have used for nearly three years: Engage in a choreographed campaign of presidential tweets, Fox News appearances and fiery congressional testimony to create expectations about finding proof of a “deep state” campaign against Mr. Trump. And then, when the proof does not emerge, skew the results and prepare for the next opportunity to execute the playbook.
That opportunity has arrived in the form of an investigation by a Connecticut prosecutor ordered this year by Attorney General William P. Barr — and the president and his allies are now predicting it will be the one to deliver damning evidence that the F.B.I., C.I.A. and even close American allies conspired against Mr. Trump in the 2016 election.
Mr. Barr made clear his thoughts on the inspector general’s report on Monday in a blistering public statement in which he described how the F.B.I. in 2016 “launched an intrusive investigation of a U.S. presidential campaign on the thinnest of suspicions” and carried out surveillance “deep into President Trump’s administration.”
He chose to leave out the fact that the inspector general had found that the F.B.I. had solid reason to open its investigation, choosing instead to say that in his view there was insufficient reason “to justify the steps taken.”
The attorney general’s comments echoed his statements after the conclusion of the investigation by Robert S. Mueller III, the special counsel. In a significant political victory for Mr. Trump, the special counsel found that there was no criminal conspiracy between the Trump campaign and Russia, and did not make a judgment about whether Mr. Trump had obstructed justice.
But Mr. Barr went further, suggesting that the president had been a victim of America’s law enforcement machinery and pledging to investigate the origins of the inquiry.
The man he has asked to lead that investigation, John H. Durham, the United States attorney in Hartford, Conn., chummed the waters on Monday by releasing a highly unusual statement saying he disagreed with some of the findings of the inspector general’s report and had a mandate to conduct a broader, more thorough investigation.
Mr. Durham is carrying out his inquiry in the heat of a presidential campaign, raising the prospect that Mr. Trump could seize on his findings should they come out in the months or weeks before the 2020 election.
The strategy on display Monday was first used by the president and his allies in March 2017, when Mr. Trump tweeted that the Obama administration had used the F.B.I. to wiretap Trump Tower during the presidential campaign.
The tweet caused a sensation among the president’s supporters, and Representative Devin Nunes, a California Republican who was then the chairman of the House Intelligence Committee, pledged to investigate. Months later, the Justice Department told a federal court that the claim was unsubstantiated, but the damage was done.
Mr. Trump eventually told Sean Hannity of Fox News that the claim in the tweet was based on “a little bit of a hunch and a little bit of wisdom.” The fact that it became such a controversy, the president brazenly asserted, was actually evidence of F.B.I. misdeeds.
“If they weren’t doing anything wrong, it would’ve just gotten by,” he said. “Nobody would have cared about it.”
In early 2018, Republicans fueled speculation that the release of a document written by Mr. Nunes would prove widespread F.B.I. surveillance abuses during the 2016 campaign and show how the bureau opened its Russia investigation based on a dossier of uncorroborated information provided by a former British spy, Christopher Steele.
Mr. Trump’s allies used the F.B.I.’s objections to the release of the Nunes memo to promote a Twitter campaign —#releasethememo — and in February of last year Mr. Trump ordered it declassified.
It landed mostly with a thud, and it even ended up debunking the claim that the dossier was the origin of the F.B.I..’s Russia investigation. The Nunes memo confirmed press reporting — that the investigation began after a Trump campaign aide told an Australian diplomat that the Russian government had obtained thousands of emails from Mr. Trump’s Democratic opponent, Hillary Clinton.
But the president’s allies soon found another opportunity: the Justice Department’s announcement of an investigation into the origins of the Russia inquiry led by Mr. Horowitz. It would be this investigation, they predicted, that would reveal the depths of the F.B.I.’s perfidy.
During a congressional hearing in September, one Republican lawmaker asked Corey Lewandowski, Mr. Trump’s former campaign manager, where he thought the “whole lie of Russian collusion started.”
Mr. Lewandowski replied that he expected Mr. Horowitz would get the answer — that it “began at the highest levels of the government and was perpetrated through the intelligence community to come up with a narrative of why Hillary Clinton lost the campaign as opposed to the real narrative, why Donald Trump won the campaign.”
Mr. Horowitz’s report made no such conclusions, even if it did criticize F.B.I. officials for serial mistakes in their applications to carry out surveillance of a Trump campaign aide.
“That so many basic and fundamental errors were made by three separate, handpicked teams on one of the most sensitive F.B.I. investigations that was briefed to the highest levels within the F.B.I., and that F.B.I. officials expected would eventually be subjected to close scrutiny, raised significant questions regarding the F.B.I. chain of command’s management,” the report said.
But the report did not find a widespread, anti-Trump conspiracy inside the F.B.I., and it even contained damning information about how some agents working on the case hoped that Mr. Trump would win a surprise victory over Mrs. Clinton.
Polls show that the relentless, White House-led assault on America’s law enforcement machinery has had an impact — especially among Republicans — but the returns might be diminishing.
In polling by the Pew Research Center last year, less than half of Republicans had a favorable view of the F.B.I., a sharp decline from previous years. In a September poll, however, two-thirds of Republicans again said they have a favorable view of the F.B.I.
It is uncertain when Mr. Durham will conclude his investigation, but Mr. Barr has given him a wide aperture to examine the work of the law enforcement and intelligence officials in 2016, and even to examine whether close American allies collaborated in an effort to elect Mrs. Clinton.
Mr. Barr and Mr. Durham traveled to Italy to examine whether the Italian government played a role in setting up a meeting between a Russia-linked professor and a Trump campaign aide, and Mr. Trump pressed Ukraine’s president and Australia’s prime minister to help Mr. Durham.
There is no indication that Mr. Durham will exhume any information that will fundamentally change the understanding of what happened in 2016. But for Mr. Trump and his allies, the final conclusions might ultimately be less important than the months spent speculating about what those conclusions might be.
Speaking to reporters in London last week, Mr. Trump played down expectations about the Horowitz inquiry — indicating it was only an appetizer for what’s to come.
“I do think the big report to wait for is going to be the Durham report,” he said.
“That’s the one that people are really waiting for.”