Kamala Harris questioned Donald Trump's mental state Tuesday after 78-year-old Republican's latest televised town hall veered into a bizarre, impromptu music session.

"Hope he's okay," the Democratic candidate posted on X.

Harris's campaign, which has begun to aggressively challenge Trump on his health and mental stability, said that during the late Monday event he appeared "lost, confused."

Trump's campaign spokesman Steven Cheung declared that instead "something very special" had taken place between the billionaire and the crowd.

For about half an hour, the event near Philadelphia in the key swing state of Pennsylvania was standard fare ahead of the November 5 election: Trump took friendly questions from supporters on the economy and cost of living.

With the session moderated by a loyal right-wing ally, South Dakota Governor Kristi Noem, Trump was on cruise control, although he got the election date wrong by two months, urging supporters to vote "on January 5."

After the town hall paused for two audience members who required medical attention, Trump then switched focus.

Jokingly asking whether "anybody else would like to faint," Trump declared "Let's not do any more questions."

"Let's just listen to music. Let's make it into a music. Who the hell wants to hear questions, right?" Trump said.

And so they did: for more than half an hour, the Trump playlist blasted while the candidate mostly stood on stage listening and slowly dancing.

Trump has made a brief, jerky dance his signature at the end of rallies for years, nearly always to his exit song — the Village People's 1978 disco anthem "YMCA."

On Monday, however, he stayed on stage for nine songs, ranging from opera to Rufus Wainwright's rendition of "Hallelujah," Elvis and of course "YMCA."

And his dance routine expanded from the familiar jerky motion to a slow swaying. Often, however, he did not dance but stood in place and stared out into the crowd and sometimes pointed at people.

Trump oldest nominee ever 

Harris and Trump are locked in a dead heat, according to polls, and the election is set to be decided by seven swing states where the margins could come down to barely 10,000 votes each.

On Tuesday, Trump was set to discuss the economy in Chicago and hold a rally in Georgia, a swing state. Harris was giving an interview to popular radio host Charlamagne the God in an effort to boost her messaging to Black male voters, a part of the electorate where Trump has made gains.

With only three weeks to go, Harris has begun to home in on Trump's health and age.

She turns 60 this Sunday and last weekend released a medical report in which the White House doctor declared her "in excellent health," with the "physical and mental resiliency" to serve as president.

Trump, the oldest person ever to be nominated for a presidential bid, has not released a recent comprehensive report on his state of health, prompting fierce criticism from Harris.

Her campaign immediately pounced on the town hall episode, posting a video on X and writing: "Trump appears lost, confused, and frozen on stage as multiple songs play for 30+ minutes and the crowd pours out of the venue early."

In a string of posts published on his own Truth Social platform just before 1am after the Pennsylvania town hall, Trump lashed back at Harris.

He pronounced he was "far healthier" than the last four US presidents and "far too busy campaigning", apparently to undergo a new health test.

He called Harris "desperate" for saying he should provide reports to the American people and said "she is dying to see my Cholesterol (which is 180!)."