While Ms. Harris was speaking, he took to his social media platform, Truth Social, to provide real-time commentary.
His posts there, capitalized in a haphazard manner, were less directed at her specific remarks than at broader complaints about issues that Mr. Trump wants to keep the focus on: crime, immigration and the economy.
At times, he digressed.
"WHERE'S HUNTER?" Mr. Trump asked as Ms. Harris came onstage, reviving one of his favorite slogans about the son of President Biden, who withdrew his candidacy weeks ago.
At one point, referring to Ms. Harris, Mr. Trump asked, in all capital letters, "Is she talking about me?" (She was, often.)
Mr. Trump also accused Ms. Harris's running mate, Gov. Tim Walz of Minnesota, of puffing up his rsum as a leader of a high school football team. "Walz was an ASSISTANT Coach, not a COACH," he wrote.
Several times during his tv appearance, the Fox anchors Bret Baier and Martha MacCallum tried to interject to ask a question. Several times, Mr. Trump ignored them. "Mr. President, let me interrupt," Mr. Baier pleaded at one point. Mr. Trump kept talking.
The call-in - which lasted for 10 minutes, until Fox News informed Mr. Trump that the network had run out of time - was hastily arranged.
At several points during the call, a familiar beeping sound interrupted Mr. Trump's remarks. It appeared that the former president was accidentally pressing buttons on the keypad of his phone.
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