Vice President Kamala Harris and former President Donald Trump.
CNN  — 

Vice President Kamala Harris turns 60 on Sunday – and, her campaign wants voters to know, that makes her 18 years younger than Donald Trump.

Harris’ campaign is increasingly questioning the former president’s mental and physical fitness in the final weeks of the 2024 presidential race.

“He’s becoming increasingly unstable and unhinged, and it requires that response,” Harris told reporters Saturday in Detroit. “I think the American people deserve better than someone who actually seems to be unstable.”

It’s a reversal of the strategy Republicans, led by Trump, used to attack President Joe Biden for years – and a remarkable turnaround for Democrats after the 81-year-old incumbent dropped out of the race in July.

Harris herself has pointed to age repeatedly in recent days to differentiate herself from Biden – and, implicitly, the 78-year-old Trump, too.

“I represent a new generation of leadership,” Harris said in an interview with Fox News on Wednesday.

“It’s a new generation of thinking, as much as anything else,” she told NBC News two days later.

Harris’ campaign on Friday seized on a Politico report that a Trump adviser had told “The Shade Room,” a podcast the former president was considering going on for an interview, that he would not do so because he was “exhausted” and declining interviews. Trump’s campaign denied he was exhausted, without addressing the back-and-forth with the podcast.

Harris senior adviser David Plouffe told CNN’s Dana Bash on Friday that the Politico report “raises real questions if somebody can’t handle the campaign trail because they’re so exhausted, whether they’re fit to be president.”

Harris’ campaign also launched a new television advertisement Thursday describing the prospect of a second Trump term in the Oval Office as “more unhinged, unstable and unchecked.”

Harris told reporters ahead of a campaign stop in Grand Rapids, Michigan, on Friday that she thinks it’s a “legitimate question” whether Trump is “fit to do the job” of president, pointing to him turning down multiple high-profile media appearances.

“I’ve been hearing reports that his team, at least, is saying he’s suffering from exhaustion, and that’s apparently the excuse for why he’s not doing interviews. And, of course, he’s not doing the CNN town hall. He refuses to do another debate,” Harris said. “And, you know, look, being president of the United States is probably one of the hardest jobs in the world, and so we really do need to ask: If he’s exhausted being on the campaign trail, is he fit to do the job?”

She also cited former Trump administration officials who have opposed the former president’s bid for another term.

The Democratic emphasis on a report about Trump being exhausted comes a week after Harris’ campaign released a letter from her doctor detailing her medical history. Harris then immediately blasted Trump for not disclosing as much detail about his own health.

CNN has reached out to Trump’s campaign for comment about Harris’ questioning of his fitness for office.

Top Harris allies have also leaned into the strategy of casting Trump as old and mentally unfit in recent days.

Harris’ running mate, Minnesota Gov. Tim Walz, while campaigning last week in Pittsburgh, pointed to a recent episode in which the former president abruptly cut off a planned town hall and played music for his supporters, again suggesting Trump is mentally unfit to serve.

“It was strange, but if this was your grandfather, you would take the keys from him,” Walz said.

Former President Barack Obama, as he campaigned for Harris in Arizona on Friday, told a Tucson crowd that America doesn’t need to see what an “older, loonier Donald Trump looks like, with no guardrails.”

Obama mocked Trump’s speeches, including his repeated references to the “late, great Hannibal Lecter,” the cannibal villain from the movie “The Silence of the Lambs.”

“Have you seen him lately? I mean, he is out there, he’s giving two-, two-and-a-half-hour speeches, just word salads. You have no idea what he’s talking about,” Obama said. “He’s talking about Hannibal Lecter, he’s talking about this, he’s talking about that.”

Trump, at times, seems to tie migrants who seek asylum in the United States to the character of Lecter being detained at an insane asylum. He hasn’t explained why he draws such a connection. However, he has also repeatedly and without evidence claimed that foreign governments are “emptying out insane asylums” to send migrants to the US-Mexico border. It’s not clear whether Trump is conflating insane asylums and the legal process of seeking asylum – two things that are entirely unrelated.

Obama also criticized Trump for referring to the January 6, 2021, riot at the US Capitol as “a day of love,” and for declaring himself the “father of IVF,” referring to in vitro fertilization. “I do not know what that means. You do not either,” Obama said of his successor.

“You would be worried if your grandpa was acting like this,” Obama said. “So, imagine it coming from a guy who wants to be given unchecked power.”

CNN’s Veronica Stracqualursi, Aaron Pellish, Ebony Davis, Andrew Millman and Betsy Klein contributed to this report.