WASHINGTON — The Biden administration revealed on Thursday that a business associate of Trump campaign officials in 2016 provided campaign polling data to Russian intelligence services, the strongest evidence to date that Russian spies had penetrated the inner workings of the Trump campaign.
The revelation, made public in a Treasury Department document announcing new sanctions against Russia, established for the first time that private meetings and communications between the campaign officials, Paul Manafort and Rick Gates, and their business associate were a direct pipeline from the campaign to Russian spies at a time when the Kremlin was engaged in a covert effort to sabotage the 2016 presidential election.
Previous government investigations have identified the Trump aides’ associate, Konstantin V. Kilimnik, as a Russian intelligence operative, and Mr. Manafort’s decision to provide him with internal polling data was one of the mysteries that the special counsel, Robert S. Mueller III, sought to unravel during his two-year investigation into Russia’s election meddling.
“During the 2016 U.S. presidential election campaign, Kilimnik provided the Russian Intelligence Services with sensitive information on polling and campaign strategy,” the Treasury Department said in a news release. “Additionally, Kilimnik sought to promote the narrative that Ukraine, not Russia, had interfered in the 2016 U.S. presidential election.”
The Biden administration provided no supporting evidence to bolster the assessment that the Russian intelligence services obtained the polling data and campaign information. And the release shed no light on why Mr. Manafort and Mr. Gates gave polling data to Mr. Kilimnik, although previous government reports have indicated that Mr. Manafort thought Trump campaign strategy information could be a valuable commodity for future business deals with Kremlin-connected oligarchs.
Having the polling data would have allowed Russia to better understand the Trump campaign strategy — including where the campaign was focusing resources — at a time when the Russian government was carrying out its own efforts to undermine Donald J. Trump’s opponent.
Mr. Gates said in a statement on Thursday that the Treasury Department had failed to provide any evidence to back up its claim, adding that “the polling data passed periodically to Kilimnik at Paul Manafort’s direction was simplistic and outdated, never in real time.”
“It was from both public and internal sources,” Mr. Gates said. “It was not massive binders full of demographics or deep research. It was ‘topline’ numbers and did not contain any strategic plans.”
The new sanctions against Russia are in response to the Kremlin’s election interference, efforts to hack American government agencies and companies, and other acts of aggression against the United States.
The sanctions now make it extremely difficult for Mr. Kilimnik, who was indicted by the Justice Department in 2018 on charges of obstruction of justice, to engage in financial transactions that may involve the United States.
It is unclear how long American spy agencies have held the conclusion about Mr. Kilimnik. Senior Trump administration officials, fearing Mr. Trump’s wrath, repeatedly tried to keep from the public any information that seemed to show Mr. Trump’s affinity for Russia or its president, Vladimir V. Putin.
Mr. Kilimnik had been a longtime business partner during Mr. Manafort’s time as a political consultant in Ukraine. In 2018, prosecutors for Mr. Mueller’s office announced that Mr. Kilimnik had “ties to Russian intelligence” and that Mr. Manafort had instructed Mr. Gates to pass the polling and campaign information to Mr. Kilimnik.
The Senate Intelligence Committee went further last August in its bipartisan report that scrutinized the links between the Trump campaign and Russia — calling Mr. Kilimnik a “Russian intelligence officer.”
The report contained several significant redactions that appeared related to Mr. Manafort and Mr. Kilimnik but said that Mr. Manafort’s willingness to share the information with him “represented a grave counterintelligence threat.”
The report called the relationship between Mr. Manafort and Mr. Kilimnik “the single most direct tie between senior Trump campaign officials and the Russian intelligence services.”
The Senate report portrayed a Trump campaign stacked with businessmen and other advisers who had little government experience and “presented attractive targets for foreign influence, creating notable counterintelligence vulnerabilities.”
A New York Times article in 2017 said that there had been numerous interactions between the Trump campaign and Russian intelligence during the year before the election. F.B.I. officials had disputed the report, but both the Senate report and the Treasury Department document confirm the article’s findings.
The assertion that it was Ukraine, not Russia, that sought to disrupt the 2016 election has long been both a Kremlin talking point and a claim by Mr. Trump that foreign actors tried to help his opponent, Hillary Clinton, rather than him.
Mr. Trump’s obsession over Ukraine’s supposed role in the election was the impetus for a 2019 phone call with the Ukrainian president that was central to the first impeachment proceedings against Mr. Trump.
Mr. Manafort was brought into the Trump campaign in March 2016, at a time when Mr. Trump had largely sewn up the Republican presidential nomination.
Mr. Manafort and his longtime business associate, Mr. Gates, joined the Trump campaign after years of doing political consulting work in Ukraine, where they met Mr. Kilimnik, a Russian Army-trained linguist.
The two men met with Mr. Kilimnik several times after joining the campaign, and in June 2016, Mr. Manafort became the Trump campaign chairman.
Details about Mr. Manafort’s relationship with Mr. Kilimnik were revealed in 2018 as the government prosecuted Mr. Manafort and charged Mr. Kilimnik with obstruction of justice for trying to coach potential witnesses in the investigation.
Mr. Kilimnik never came to the United States to face charges. He is wanted by the F.B.I., and the bureau is offering $250,000 for information that could lead to his arrest.