One of Paul Manafort’s clients in Ukraine appears to have laid the foundation for theories of Ukrainian interference in the 2016 election that are now at the heart of President Trump’s pressure campaign on Kyiv, according to an FBI interview released on Friday.

The interview notes say that Ukrainian politician Serhiy Lyovochkin — Manafort’s longtime client in Kyiv — told the former Trump campaign chairman that the U.S. Embassy in Kyiv had demanded information about Manafort from a specialized anti-corruption law enforcement body.

The notes came out in FOIA litigation pursued by Buzzfeed and CNN, which has pried open redacted copies of FBI interview notes from the Mueller investigation.

In this interview, Manafort told the special counsel that Lyovochkin had “heard from Ukrainian President Petro Poroshenko that the U.S. Embassy was pressuring Ukraine’s National Anti-Corruption Bureau for information on Manafort.”

TPM reported last month that the pressure campaign on Ukraine which led to the third impeachment in U.S. history began largely because of a belief among Trump and his allies that Manafort had been the target of a Ukrainian plot to damage Trump’s chances in the 2016 election.

Specifically, the theory boils down to an August 2016 New York Times article reporting that Manafort’s name appeared next to $12.7 million in alleged bribes on a ledger belonging to the political party for which he consulted while working in Ukraine.

The article forced Manafort’s resignation from Trump’s campaign, and cited statements from Ukraine’s National Anti-Corruption Bureau, which was investigating the ledger.

The bureau was set up during the Obama administration as a specialized anti-corruption prosecutor with access to help from the FBI, in theory giving it an edge in probing the kind of financial crime that bedevils Ukraine.

But to Trump and his allies, the suggestion that a Ukrainian law enforcement body released damaging information about the Trump campaign’s chairman constituted an example of “election interference” during 2016.

Giuliani himself reportedly consulted with Manafort’s legal team about the allegations, and has said that he began pushing Ukraine for investigations out of a desire to probe Ukraine’s “interference” in 2016.

The FBI interview notes suggest that the genesis of the theory came directly through Manafort from his Ukrainian client.

Ukrainian efforts to sabotage Trump campaign – "quietly working to boost Clinton." So where is the investigation A.G. @seanhannity — Donald J. Trump (@realDonaldTrump) July 25, 2017

Poroshenko, the predecessor of current Ukrainian President Volodymyr Zelensky, faced tough headwinds after Trump was elected, being forced to cope with a U.S. President who believed that Ukraine had lashed out against his Presidential campaign.