Is this thing on? Harris and Trump battle over hot mics at debate. POLITICOTrump campaign casts fresh doubt on September debate with Harris over microphone dispute CNNTrump Hints He May Ditch Debate as Rules Negotiations Stall Rolling StoneElection Live Updates: Debate Over Presidential Debate Rules Resumes The New York TimesDonald Trump threatens to pull out of 10 September presidential debate The Guardian US