Kamala Harris has attacked Donald Trump as a threat to individual freedom, economic security and the rule of law in the US since launching her White House campaign nearly two weeks ago.

But the vice-president and her Democratic allies have found a novel way of describing Trump and the Republican party that is unnerving their opponents: describing them as “weird”.

“Some of what he and his running mate are saying, it’s just plain weird,” Harris said during a fundraiser last weekend, as the audience laughed. “I mean, that’s the box you put that in, right?”

Democrats have been trying to portray Trump and his followers as part of an extreme rightwing fringe of American politics for years, including after the January 6 2021 attack on the US Capitol, with mixed success.

But the hardline views on abortion and disparaging comments on women by Trump’s running mate, Ohio senator JD Vance, have highlighted a fresh line of attack from the Democrats. Quips such as Vance’s in a 2021 speech that America was run by “childless cat ladies” have gone viral online, turbocharging the new strategy.

“These are weird people on the other side, they want to take books away, they want to be in your exam room, that’s what it comes down to,” Tim Walz, the Democratic governor of Minnesota and contender to be Harris’s running mate, told MSNBC two days after she entered the race.

An independent Harris supporters group called “Won’t Pac Down” last month launched an ad called “these guys are just weird” that has since gone viral featuring a series of creepy male “Maga Republicans” saying they want the “government way more involved in your sex life”.

“These opinions that mainstream Republicans in a lot of cases are holding, are honestly just bizarre,” said Travis Helwig, a television producer who created the ad, which is aimed at younger voters.

He added the attack appears to be resonating because while Trump and his allies “enjoy being called threats to democracy”, “‘weird’ is clearly getting under their skin” more.

“It does seem like they’re spiralling a little,” he added.

Trump and his allies have failed to find an effective response. During his appearance at a conference for black journalists in Chicago this week, the Republican former president oddly questioned Harris’ Black identity, saying it was contrived, triggering a fierce backlash from across the political spectrum.

By Thursday, he was on a conservative podcast trying to defend himself. “I’m a lot of things, but weird I’m not,” Trump said. 

Republicans are instead accusing Democrats of being petty and hypocritical. “This whole ‘they’re weird’ argument from the Democrats is dumb & juvenile. This is a presidential election, not a high school prom queen contest,” Vivek Ramaswamy, the former biotech investor who ran for the Republican nomination but dropped out and endorsed Trump, wrote on X. 

Democrats have maintained their line. “If Republican leaders don’t enjoy being called weird, creepy, and controlling, they could try not being weird, creepy, and controlling,” Hillary Clinton, the former secretary of state and first lady, also wrote on X.

Martha McKenna, a Democratic strategist, said the Harris campaign’s approach reflected a change from Biden’s message. Not only is it focusing on the concept of defending “freedom” more directly, it’s also bringing some levity to the criticism.

McKenna said: “I think that the Biden campaign was really focused on the threat to democracy and very high level concepts, which are still very important and very relevant to the presidential campaign. But with this change of candidate, there comes a change of language and a moment in time where you can do a bit of a refresh.”

The Harris campaign’s shift comes as the candidate is building her team of political advisers for the dash to the November election, which is less than 100 days away.

While Harris is retaining Jen O’Malley Dillon as campaign chair — the same role she had for Biden — she has also brought in David Plouffe and Stephanie Cutter, former political advisers to Barack Obama, to help.

In addition to the ‘weird’ trope, the Harris campaign continues to focus on serious issues around the Republicans and the implications of the election.

At a fundraiser on Fire Island on Friday, Doug Emhoff, Harris’ husband, said: “We’ve got to push back on that despicable person and his little side kick,” referring to Trump and Vance respectively, and calling the Republican vice-presidential nominee an “extremist and an opportunist”. “We know who he is. He’s told us. He wants to literally just change the way that you all live, the way that we all live,” Emhoff said.

Amy Walter, an independent political analyst at the Cook Political Report with Amy Walter, said Harris is aware that while the attacks on Republican strangeness may be catchy for now, the election will probably be decided on swing voters’ perceptions of the economy.

“Harris’s first ad doesn’t talk about Trump being ‘weird’ but instead argues that Trump ‘wants to take our country backward to give tax breaks to billionaires and big corporations and end the Affordable Care Act’,” Walter wrote in a note on Friday.

Still, the jibes against Trump and his allies are expected to continue, with the line on oddness ingrained in talking points.

“[Trump] is clearly older and stranger than he was when America first got to know him,” transport secretary and possible Harris running mate Pete Buttigieg, said on Fox News Sunday last month.