“Three months ago she was thought of so badly, [the media] were just killing her,” he said of the vice-president.
“And now they’re trying to make her into a – let’s say – Margaret Thatcher. I don’t think so. It’s not going to happen.
“Margaret Thatcher didn’t laugh like that. Did she? If she did, she wouldn’t have been Margaret Thatcher,” the Republican added, labelling his rival “Laughin’ Kamala Harris”.
Just days ago, the Trump campaign attacked Ms Harris as a “Marxist fraud” as it declined to accept her invitation to a presidential debate.
It had previously agreed to two debates with Joe Biden, the president whom Ms Harris replaced as the presumptive Democratic candidate. The second was scheduled for Sept 10.
Steven Cheung, Trump’s campaign spokesman, said: “Given the continued political chaos surrounding crooked Joe Biden and the Democrat Party, general election debate details cannot be finalised until Democrats formally decide on their nominee.
“There is a strong sense by many in the Democrat Party… that Kamala Harris is a Marxist fraud who cannot beat President Trump, and they are still holding out for someone ‘better’.”
His team had previously suggested the former president was taking a statesmanlike approach since his attempted assassination attempt. Surrogates, including his son Donald Trump Jr, suggested he had been changed by the near-death experience – something Trump denied on Saturday.
“I want to be nice,” the Republican, appearing in public for the first time without a bandage on the ear that was grazed by a gunman’s bullet, said.
“They all say, ‘I think he’s changed. I think he’s changed since two weeks ago. Something affected him’.”
“No, I haven’t changed,” he added as supporters cheered. “Maybe I’ve gotten worse. Because I get angry at the incompetence that I witness every single day.”