"President Zelensky said he understood, and represented to us that he had no desire to interfere in a U.S. election. I interpreted Zelensky's answer to my question as a concession of the premise of my question—that he was receiving improper overtures from Giuliani to interfere in the 2020 election," Murphy added in the letter.

Murphy, in a letter to the leaders of the House impeachment inquiry, said he raised Giuliani,'s personal lawyer, in a meeting with the Ukraine leader in September and explained that he had heard reports that "Zelensky was being asked to become an actor in U.S. domestic politics."

Sen.(D-Conn.) said on Tuesday that he believed Ukraine President Volodymyr Zelensky was feeling pressure fromto investigate the Bidens.

Murphy added that Zelensky "did not contradict the facts I laid out in my question, and instead simply relayed his desire to say clear of becoming enmeshed in American politics. To me, this was confirmation that Zelensky was indeed feeling the pressure I described."

But Murphy, in his seven-page letter, said he learned in May that Giuliani was "running a shadow foreign policy operation in Ukraine," including trying to get the Ukraine government to probe former Vice President Biden and his son Hunter Biden.

"My concern was raised even higher when I began to hear from people who had spoken to Zelensky that he was very confused by Giuliani's requests, and worried about the possible consequences of rebuffing Trump's demands," Murphy added. In addition to bringing up Giuliani with Zelensky, Murphy says he also brought up Trump's personal lawyer with Bill Taylor, the top U.S. diplomat to Ukraine and a witness in the impeachment inquiry. Taylor, according to Murphy, called Giuliani's efforts "a problem" and said that Zelensky's team was confused about whose directive they should be following—Giuliani's or the State Department's. "At dinner, I raised with Taylor the news reports of Giuliani's shadow foreign policy operation in Ukraine, and I asked him the impact it was having on U.S.-Ukraine policy and his work at the embassy. 'It's a problem,' he told me," Murphy wrote. "At dinner, I raised with Taylor the news reports of Giuliani's shadow foreign policy operation in Ukraine, and I asked him the impact it was having on U.S.-Ukraine policy and his work at the embassy. 'It's a problem,' he told me," Murphy wrote.

Johnson, in his letter, said Vindman may be among a class of government bureaucrats who aim to push back on Trump’s policies “by leaking to the press and participating in the ongoing effort to sabotage his policies and, if possible, remove him from office.”