Johnson’s letter comes after the top Republican on the House Oversight Committee, Jim Jordan of Ohio, and Intelligence Committee ranking member Devin Nunes (R-Calif.) requested that the Wisconsin Republican provide firsthand knowledge of Trump's actions toward Ukraine between this April and September .

Johnson joined a delegation to Ukraine with Energy Secretary Rick Perry, the U.S. envoy to Ukraine Kurt Volker, Gordon Sondland, the former U.S. ambassador to the European Union and Vindman in May and later discussed the trip with Trump.

In his letter, Johnson recalled that Vindman said on the trip that it was the NSC’s position that the United States’ relationship with Ukraine remain "separate from our geopolitical competition with Russia," a point Johnson questioned.

Sen. Ron Johnson. | Alex Wong/Getty Images

Johnson, who chairs both the Senate Homeland Security Committee and the Senate Foreign Relations Committee’s European subcommittee, further recalled meeting with Trump after attending Zelensky’s inauguration. Johnson wrote that he could not recall Trump mentioning the Biden family, or Burisma, the Ukrainian gas company Biden’s son Hunter worked for.

Johnson wrote that he was not aware of the president telling the delegation to work with his personal lawyer Rudy Giuliani, as Sondland testified to House impeachment investigators.

The Wisconsin Republican also recalled another conversation with the president, when he was asked about whether the administration’s hold on $250 million in aid to Ukraine could be lifted in the lead-up to his September trip to Ukraine.

“The president was not prepared to lift the hold, and he was consistent in the reasons he cited,” Johnson wrote. “He reminded me how thoroughly corrupt Ukraine was and again conveyed his frustration that Europe doesn’t do its fair share of providing military aid.”

Johnson recalled that when he met with Zelensky in September along with Sen. Chris Murphy (D-Conn.), the Ukrainian president never mentioned that he or any Ukrainian felt pressure to provide the United States with anything in return for the aid. Republicans have attempted to discredit the House impeachment investigation by citing that Zelensky has never publicly indicated he felt pressure from Trump.

Johnson concluded his letter by questioning the motivations of the whistleblower who raised concerns about Trump’s July 25 call that helped spark the impeachment inquiry, writing that “not all whistleblowers are created equal.”

“If the whistleblower’s intention was to improve and solidify the relationship between the U.S. and Ukraine, he or she failed miserably,” Johnson wrote. “ All the complaint has accomplished is to fuel the House’s impeachment desire (which I believe was the real motivation), and damage our democracy.”

