Anderson Cooper 360

Morrison Says He Had No Concerns About Pres. Trump's July 25 Call, While Volker Says He Wasn't Involved In Bribery; Ex-Ukraine Enovy Changes Past Testimony, Now Says Push To Investigate Burisma Connected To Biden; Volker Says He Found The Reference To Biden During Pres. Trump's July 25 Call Unacceptable; Key Witnesses Say They've Never Seen Aid Withheld "Because The President Wanted His Rival Investigated"; Morrison: Investigating The Bidens "Was Not A Policy Objective"; Volker: What Giuliani Was Saying About Ukraine Was A "Problem"; Morrison: Investigating The Bidens "Was Not A Policy Objective"; Ex-Ukraine Envoy Changes Past Testimony, Now Says Push To Investigate Burisma Connected To Biden; Volker: What Giuliani Was Saying; Ex-White House Aide: Highly Unusual Effort To "Lock Down" Transcript Of July 25 Call Was An "Administrative Error"; Ex-Envoy Says He Should Have Recognized Push For Probe Into Ukrainian Company Was Connected