This time, Russian intelligence operatives deployed a network of agents to blame Ukraine for its 2016 interference. Starting at least in 2017, the operatives peddled a mixture of now-debunked conspiracy theories along with established facts to leave an impression that the government in Kyiv, not Moscow, was responsible for the hackings of Democrats and its other interference efforts in 2016, senior intelligence officials said.

The Russian intelligence officers conveyed the information to prominent Russians and Ukrainians who then used a range of intermediaries, like oligarchs, businessmen and their associates, to pass the material to American political figures and even some journalists, who were likely unaware of its origin, the officials said.

That muddy brew worked its way into American information ecosystems, sloshing around until parts of it reached Mr. Trump, who has also spoken with Mr. Putin about allegations of Ukrainian interference. Mr. Trump also brought up the assertions of Ukrainian meddling in his July 25 call with President Volodymyr Zelensky of Ukraine, which is at the heart of the impeachment inquiry into whether he abused his power by asking for a public commitment to investigations he stood to gain from personally.