Former U.S. special envoy to Ukraine Kurt Volker and former National Security Council Russia adviser Tim Morrison — two witnesses called by Republicans — testified Tuesday afternoon in the second public impeachment hearing of the day.

The big picture: Volker was part of a cadre of officials who worked with Rudy Giuliani to push Ukraine to announce investigations into Trump's political rivals, though he testified Tuesday that he was not aware that the investigation would involve Joe Biden. Morrison testified that EU Ambassador Gordon Sondland informed him that nearly $400 million in military aid to Ukraine would be released if Ukrainian President Volodymyr Zelensky announced the investigations.

Highlights

In his opening statement, Volker testified that he did not understand until recently that a proposed Ukrainian investigation of the gas company Burisma — where Hunter Biden formerly served on the board — was equivalent to an investigation of the Bidens. He added that if he had known that was the case, he would have raised objections.

Volker testified that allegations by Ukraine's former prosecutor general against Joe Biden and former U.S. Ambassador to Ukraine Marie Yovanovitch are baseless and that he knows both to be honorable people.

Volker also said in his opening statement that he was not aware of a linkage between military aid and Zelensky's announcement of investigations and that he opposed the hold on security assistance. He said that he warned Zelensky that Rudy Giuliani was negatively influencing Trump's view of Ukraine.

In a major change from his closed-door testimony, Volker said that Sondland raised "investigations" in a meeting with Ukrainian officials in the White House and that he and others present thought it was inappropriate. Volker said that it would be appropriate to ask Ukraine to investigate the 2016 election and Burisma, but that the meeting at the White House was not the right time or place for Sondland to do so.

Of note: At this point, Volker said he had made a “distinction” between an investigation of Burisma and an investigation into the Bidens.

At this point, Volker said he had made a “distinction” between an investigation of Burisma and an investigation into the Bidens. Morrison testified that he recommended that access to the Trump-Zelensky call transcript be restricted, but that its placement onto a highly classified computer system was an "administrative error."

Morrison testified that Sondland informed him on Sept. 7 that a hold on Ukraine military aid would be released if Zelensky announced investigations into Biden and the 2016 election. Morrison stated that he got a "sinking feeling" and reported his concerns to then-national security adviser John Bolton, who told him to notify White House lawyers.

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