regular channel, the regular channel atop which sits donald trump, the vice president, the secretary of state, rudy giuliani is swirling around and contaminating some of it, but that was the policy. not a single witness, republican or democratic, has disputed that fact, ever. >> reporter: no. and i think the last couple of pillars of the republican defense that are still standing to some degree here, and i think we'll see them fall back on here, are the questions, does biden equal burisma. here you see career staffers, experts in ukraine, who are very quick to make that connection whereas some of the political appointees were slower to make that connection. does biden equal burisma in terms of investigations, to what degree is rudy giuliani speaking for the president when he's speaking for the president. i think those will be the key things here. and whether or not the withholding of aid was conditioned on the investigations or whether it speaks to the president's, you know, long held concerns about ukraine. those are the three things left i think we will hear republicans hit over and over and over again