American intelligence officials were concerned that Russian intel attempted to use President Trump's personal lawyer Rudy Guiliani in an influence campaign. That's according to The Washington Post.
Guiliani visited Ukraine in December of 2019 during the impeachment investigation. But intelligence officers provided written warnings to the White House even earlier. National security adviser Robert O'Brien led the efforts warning President Trump about the influence campaign, saying that any information provided by Guiliani after those trips are tainted by Russia.