WASHINGTON — When the Trump administration assigned a prosecutor in 2019 to scour the Russia investigation for any wrongdoing, President Donald J. Trump stoked expectations among his supporters that the inquiry would find a “deep state” conspiracy against him.

Three years later, the team led by the special counsel, John H. Durham, on Monday will open the first trial in a case their investigation developed, bringing before a jury the claims and counterclaims that surrounded the 2016 presidential campaign. But rather than showing wrongdoing by the F.B.I., it is a case that portrays the bureau as a victim.

The trial centers on whether Michael Sussmann, a cybersecurity lawyer with ties to Democrats, lied to the F.B.I. in September 2016, when he relayed suspicions about possible cyberconnections between Mr. Trump and Russia. The F.B.I. looked into the matter, which involved a server for the Kremlin-linked Alfa Bank, and decided it was unsubstantiated.

In setting up the meeting, Mr. Sussmann had told an F.B.I. official that he was not acting on behalf of any client. Prosecutors contend he concealed that a technology executive and the Hillary Clinton campaign were his clients to make the allegations seem more credible.

The defense argues that Mr. Sussmann was not acting on their behalf at the meeting. The F.B.I. was aware that he had represented Democrats on matters related to Russia’s hacking of their servers, and subsequent communications made clear that he also had a client who had played a role in developing the data analysis concerning Alfa Bank, his lawyers say.

While the charge against Mr. Sussmann is narrow, Mr. Durham has used it to release large amounts of information to insinuate that there was a broad conspiracy involving the Clinton campaign to essentially frame Mr. Trump for colluding with Russia.

That insinuation also hangs over the other case Mr. Durham has developed, which is set to go to trial later this year. It accuses a researcher for the so-called Steele dossier — a since-discredited compendium of opposition research about purported links between Mr. Trump and Russia — of lying to the F.B.I. about some of his sources.

Both cases have connections with the law firm Perkins Coie, where Mr. Sussmann worked then. One of his partners, Marc Elias, was the general counsel of the Clinton campaign and had commissioned opposition research that led to the Steele dossier.

The Alfa Bank allegations and the Steele dossier were largely tangential to the official investigation into whether there was collusion between Russia and the Trump campaign. F.B.I. officials had opened that investigation on other grounds, and the special counsel who completed the inquiry, Robert S. Mueller III, did not rely on either in his final report.

(His report detailed “numerous links between the Russian government and the Trump campaign,” but he did not charge any Trump associate with a criminal conspiracy with Russia.)

But supporters of Mr. Trump have rallied around Mr. Durham’s narrative, which resonates with Mr. Trump’s oft-repeated claim that the entire Russia investigation was a “hoax.”

Defense lawyers for Mr. Sussmann have also rejected prosecutors’ broader insinuations about the constellation of events that led to his indictment, accusing the Durham team of fueling politicized conspiracy theories.

Against that backdrop, much of the pretrial jostling has centered on how far afield prosecutors may roam from the core accusation. Judge Christopher Cooper of the Federal District Court for the District of Columbia, an Obama appointee, has imposed some limits on what Mr. Durham’s team may present to the jury.

Through his court filings, Mr. Durham and his team have signaled that they suspect that the Alfa Bank data or analysis may have been faked, even though they were unable to prove it.

But the judge barred Mr. Durham from presenting evidence or arguments along those lines, saying that unless there was proof Mr. Sussmann had reason to doubt the data when it was brought to him, there should not be “a time-consuming and largely unnecessary mini-trial to determine the existence and scope of an uncharged conspiracy.”

Still, the judge has given prosecutors broader latitude to call witnesses associated with the Clinton campaign, including Mr. Elias and Robby Mook, the campaign manager.

The Alfa Bank issue traces back to the spring of 2016, when it came to light that Russia had hacked Democrats.

That summer, as suspicions escalated about Mr. Trump’s relationship with Moscow, a group of data scientists identified odd internet data that appeared to link servers for the Trump Organization to Alfa Bank.

Working with Rodney Joffe, a technology executive and cybersecurity expert, they theorized that it might be a covert communications channel. Mr. Joffe, who was already client of Mr. Sussmann’s, brought the matter to him, and Mr. Sussmann relayed those suspicions to reporters and the F.B.I. He also told Mr. Elias about it, and Clinton campaign officials were apparently aware that he was trying to get reporters to write about it.

Seeking a meeting with the F.B.I. to share the material, Mr. Sussmann reached out to James A. Baker, then the agency’s top lawyer. Mr. Sussmann said in a text that he was not bringing it on behalf of any client and was motivated by a desire to help the bureau. Mr. Baker is expected to be a primary prosecution witness.

But Mr. Durham’s team obtained law firm billing records showing that Mr. Sussmann had logged time working on the Alfa Bank suspicions to the Clinton campaign. The team argued that he lied because if the F.B.I. knew of the political connection, agents might have treated the matter differently.

“The strategy, as the government will argue at trial, was to create news stories about this issue, about the Alfa Bank issue,” Andrew DeFilippis, a prosecutor for Mr. Durham, said at a recent hearing. “And second, it was to get law enforcement to investigate it; and perhaps third, your honor, to get the press to report on the fact that law enforcement was investigating it.”

At the same hearing, a defense lawyer, Sean Berkowitz, said that he would not contest that Mr. Sussmann represented the Clinton campaign in telling reporters about those allegations. But he suggested that the defense would contend that Mr. Sussmann did not believe he was taking the matter to the F.B.I. “on behalf” of the campaign or Mr. Joffe.

Mr. Berkowitz noted that Mr. Sussmann had told Mr. Baker that he believed The New York Times planned to publish an article on the Alfa Bank suspicions, which was why he was reaching out.

“We expect there to be testimony from the campaign that, while they were interested in an article on this coming out, going to the F.B.I. is something that was inconsistent with what they would have wanted before there was any press,” Mr. Berkowitz said. “And in fact, going to the F.B.I. killed the press story, which was inconsistent with what the campaign would have wanted.”

Some details of that matter remain murky. Mr. Baker has testified that the F.B.I. tried to ask The Times “to slow down” on publishing. But news reports indicate that editors were not ready to run that article, which was being written by the reporter Eric Lichtblau, although the paper published one mentioning Alfa Bank six weeks later.

Defense lawyers have also argued that even if Mr. Sussmann lied, it would have been immaterial because the F.B.I. would have still investigated the allegations. And they have suggested that despite his initial statement, Mr. Sussmann was open about having a client in subsequent communications. Notes of a March 2017 F.B.I. meeting with Mr. Baker show that the bureau understood he had one by then.

The defense has also subpoenaed Mr. Lichtblau, who is no longer at The Times, to testify. A lawyer for Mr. Lichtblau has asked the judge to limit questioning to his discussions with Mr. Sussmann, avoiding other confidential sources and journalistic matters. Mr. Durham’s team is expected to object to any such constraint.