WASHINGTON >> A Russian analyst who contributed to a dossier of Democratic-funded research into ties between Russia and Donald Trump was arrested today on charges of lying to the FBI about his sources of information, among them an associate of Hillary Clinton.

The case against Igor Danchenko is part of special counsel John Durham’s ongoing investigation into the origins of the FBI’s probe into whether Trump’s 2016 campaign and Russia had conspired to tip the outcome of that year’s presidential campaign.

The indictment, the third criminal case brought by Durham and the second in a two-month span, is likely to boost complaints from Trump allies that well-connected Democrats worked behind the scenes to advance suspicions about Trump and Russia that contributed to the FBI’s election-year investigation.

The case does not undercut investigators’ findings that the Kremlin aided the Trump campaign —findings that were not based on the dossier. But it does endorse a longstanding concern about the Russia probe: that opposition research the FBI relied on was marred by unsupported, uncorroborated claims.

The five-count indictment accuses Danchenko of making multiple false statements to the FBI when interviewed in 2017 about his role in collecting information for Christopher Steele, a former British spy who was paid by Democrats to investigate connections between Trump and Russia.

Danchenko, a U.S.-based Russian who’d specialized in Russian and Eurasian matters as an analyst at the Brookings Institution think-tank, was a significant source for Steele as Steele compiled his dossier of research. That dossier, the target of intense derision from Trump, was ultimately provided to the FBI and used by federal authorities as they applied for and received surveillance warrants targeting a former Trump campaign aide.

According to the indictment, Danchenko repeatedly lied to the FBI about his sources of information and that deception mattered because the FBI “devoted substantial resources attempting to investigate and corroborate the allegations” in the dossier and had “relied in large part” on that research in obtaining the surveillance warrants.

A lawyer for Danchenko had no immediate comment.

The indictment says Danchenko misled the FBI by denying that he had discussed any allegations in the dossier with a contact of his who worked as a public relations executive and was also a longtime Democratic operative who campaigned for Clinton, Trump’s 2016 opponent.

In fact, the indictment says, Danchenko had sourced one or more allegations in the dossier anonymously to that Clinton associate, who is not named in court papers. As the FBI worked to corroborate the dossier’s allegation, it would have been important to know the Democrat’s role in feeding information for it because it bore upon his “reliability, motivations, and potential bias as a source,” according to the indictment.

Charging documents also refer to salacious and unsupported sexual allegations involving Trump’s behavior at a Moscow hotel that were included in the dossier but that Trump has vigorously disputed, including to former FBI Director James Comey.

The indictment says Danchenko told the FBI he had collected information about Trump’s activities at the hotel from multiple sources but didn’t himself know if the sexual allegations were true.

The unnamed Clinton ally had stayed at the same hotel in June 2016 and had attended meetings with Danchenko, according to the indictment. It says that had the FBI known that the Democrat was a source for Danchenko, the bureau could have interviewed him about the Moscow trip and whether they had discussed Trump’s own stay there.

The indictment also accuses Danchenko of lying to the FBI about a July 2016 phone call he says he had with someone he believed to be the president of the Russian-American Chamber of Commerce. That person, according to the dossier and Danchenko’s account to the FBI, told him about a “well-developed conspiracy of co-operation” between the Trump campaign and Russia. The indictment says Danchenko fabricated his account and never actually received such a phone call.

Both the dossier and the Durham probe are politically charged.

Trump’s Justice Department appointed Durham as Trump claimed the investigation of campaign ties to Russia was a witch hunt. Trump pointed to the dossier, much of which the indictment says the FBI was unable to corroborate, as evidence of a tainted probe driven by Democrats.

But the dossier had no part in launching the Trump-Russia investigation. Special counsel Robert Mueller ultimately found questionable ties between the Trump campaign and Russia, but not sufficient evidence to pursue criminal charges. Democrats have lambasted the Durham probe as politically motivated, but the Biden administration has not stopped it.

The Justice Department’s inspector general has faulted the FBI and the Justice Department for their handling of the dossier. Danchenko — who was not identified by name in the watchdog report — had told FBI investigators during a 2017 interview about the dossier’s origins and veracity that there were “potentially serious problems with Steele’s descriptions of information in his reports.”

But those qualms from Danchenko were omitted from the final three surveillance applications, making the dossier appear more credible than even one of its own sources thought it was, according to the report from Inspector General Michael Horowitz.

Danchenko has himself suggested that the information he offered to Steele was not meant to be portrayed as indisputable fact.

“Even raw intelligence from credible sources, I take it with a grain of salt,” Danchenko told The New York Times last year. “Who knows, what if it’s not particularly accurate? Is it just a rumor or is there more to it?”

The indictment is the third criminal action from Durham.

Cybersecurity lawyer Michael Sussmann was charged in September with lying to the FBI during a 2016 conversation in which he relayed concerns about potentially suspicious cyber contacts between a Trump Organization server and the server of a Russian bank. Durham’s team says he concealed from the FBI that he was presenting the concerns as a lawyer for the Clinton campaign. He has pleaded not guilty.

Last year, Kevin Clinesmith, a former FBI lawyer, admitted altering an email related to the surveillance of the Trump aide, Carter Page.