deputy to national security adviser for john bolton. he listened in on the july call where president trump wanted ukraine to investigate joe biden. the democrats are standing by the subpoena requiring kupperman to testify. zach wolf in washington. u.s. diplomat william taylor told investigators the president withheld military aid and refused to meet with ukraine's president. listen to the vice president evade giving a yes or no when he was asked if he had knowledge of the president's efforts. >> i can only tell you what i know. and what i know is that the transcript of the president's call with president zelensky, showed there was no quid pro quo and he did nothing wrong. >> were you aware of the deal