US Vice President Kamala Harris cast herself as the "underdog" in the presidential race and called her Republican opponent Donald Trump "just plain weird," while Mr Trump painted Ms Harris as "evil," "sick" and "unhinged" as the rivals exchanged barbs from afar.
The dueling appearances capped a whirlwind week that saw Ms Harris ascend to the top of the Democratic ticket after US President Joe Biden, 81, dropped his reelection bid under mounting pressure from his fellow Democrats.
A series of polls indicate that Harris' entry erased the lead Mr Trump had enjoyed over Mr Biden in a matter of days.
Ms Harris, speaking at a private fundraiser headlined by singer-songwriter James Taylor in Pittsfield, Massachusetts, said much of the rhetoric coming from Mr Trump and his running mate, US Senator JD Vance, was "just plain weird."
Her use of the word "weird" to describe her opponents was part of a new strategy from Democrats.
The Harris campaign called Mr Trump "old and quite weird" following his appearance on Fox News on Thursday, and at least one supporter showed up outside the event yesterday holding a sign proclaiming "Trump is weird."
As she did during a blitz of campaign stops this week, Ms Harris, 59, again contrasted her background as a prosecutor with Mr Trump's record as a convicted felon and said her bid was about the future, while Mr Trump, 78, wanted to return the country to a "dark past."
Hours later, Mr Trump unleashed a barrage of hyperbolic attacks at a rally in St. Cloud, Minnesota, asserting that Ms Harris would "destroy the country" and criticising her on issues ranging from public safety to immigration.
"If a crazy liberal like Kamala Harris gets in, the American dream is dead," Mr Trump said, adding that Ms Harris is "even worse" than Mr Biden.
The former president's speech - suffused with familiar grievances and false claims about election fraud - made clear that his short-lived call for unity following the attempt on his life two weeks ago had dissipated altogether.
"I want to be nice. They all say, 'I think he's changed,' Mr Trump said. "No, I haven't changed. Maybe I've gotten worse."
The former president's event at an 8,000-seat ice hockey arena complied with the US Secret Service's recommendation that he avoid large outdoor events following the assassination attempt at a Pennsylvania rally.
Mr Trump said on his Truth Social site that he would continue to hold outdoor rallies and that the Secret Service had "agreed to substantially step up their operation" to protect him.
Minnesota has not chosen a Republican presidential candidate in 52 years, but the Trump campaign had viewed it as increasingly within reach after Mr Biden's poll numbers dipped following his disastrous 27 June debate performance.
Ms Harris' takeover, however, has reenergised a campaign that had faltered badly amid Democrats' doubts about Mr Biden's chances of defeating Mr Trump or his ability to continue to govern should he succeed.
