Derkach’s dossier was not flagged for officials inside the State Department until months later, when Derkach began holding press conferences and Trump’s personal lawyer, Rudy Giuliani, reiterated the same talking points as Derkach on a range of issues. But officials inside the U.S. intelligence and national security apparatus, with the help of officials on the ground in Kyiv, had drafted reports warning that Russian proxies, including Derkach, were attempting to undermine the 2020 election process in America.

Seven current and former U.S. officials spoke with The Daily Beast about Derkach, his relationship to Trump loyalists, and the escalating warnings about Derkach’s activities. Those warnings extended to leaders on Capitol Hill who learned that Ukrainians with ties to Russia were inserting themselves in the U.S. election. Last week, the Treasury Department blacklisted Derkach as an “active Russian agent.”

The blacklisting has caused problems for one legislator in particular: Sen. Ron Johnson (R-WI), who is nearing the end of a probe into Democratic presidential nominee Joe Biden’s activities in Ukraine—specifically, the discredited notion that the then-vice president halted a corruption probe that might have interfered with his son Hunter’s business interests there. It’s a would-be controversy that’s been fueled by a nexus of Trump allies and pro-Russian Ukrainians. During Trump’s impeachment, the story was publicly discredited, but Johnson has said the imminent result of his probe will be damning for Biden. “What our investigations are uncovering, I think, will reveal this is not somebody we should be electing president of the United States,” Johnson told a local Wisconsin TV station on Tuesday.