Early in his speech in Minnesota on Saturday night, former President Donald J. Trump made clear just how quickly he has jettisoned the appeal for national unity that he made after he survived an assassination attempt in Pennsylvania two weeks ago.

“I want to be nice,” Mr. Trump said. “They all say, ‘I think he’s changed. I think he’s changed since two weeks ago. Something affected him.’”

But to a cheering crowd of thousands, Mr. Trump quickly conceded the point. “No, I haven’t changed,” he said. “Maybe I’ve gotten worse. Because I get angry at the incompetence that I witness every single day.”

Propelled by the upheaval in the presidential race caused by President Biden’s decision to end his campaign six days ago, Mr. Trump on Saturday once more escalated his attacks against Vice President Kamala Harris, now the presumptive Democratic nominee.

During a speech lasting roughly 90 minutes, Mr. Trump called Ms. Harris “evil,” “unhinged” and “sick.” He lied about her views on abortion in an effort to paint her as extreme, and he mocked her laugh and her demeanor.

“We have a brand-new victim,” Mr. Trump told thousands of people inside the Herb Brooks National Hockey Center in St. Cloud, Minn. “And, honestly, she’s a radical left lunatic.”