Barack Obama questioned Donald Trump’s stamina for high office, as he campaigned on behalf of Democratic presidential candidate Kamala Harris in the swing state of Arizona.

At a Friday rally in the city of Tucson, Obama needled Trump on his ability to serve a second term, a theme Harris and campaign surrogates have recently leaned into.

“Along with his intentions, there is also a question of his competence. Have you seen him lately?” asked Obama. “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.”

Democrats have been quick to call into question whether Trump is young enough and mentally competent enough to serve another term in the White House.

After 81-year-old President Joe Biden suspended his re-election campaign in July and was replaced at the top of the Democratic ticket with 59-year-old Vice President Harris, questions of age went from being a vulnerability for the Democrats to a potent line of attack against Trump, now the oldest presidential candidate in US history.

Those attacks have picked up over the last week, after a series of events where Trump appeared unsure of himself and media cancellations that Democrats have portrayed as proof of physical exhaustion from campaigning.

“If he can’t handle the rigours of the campaign trail, is he fit to do the job?” Harris said at a rally in the must-win state of Michigan on Friday.

Harris and allies such as Obama and his wife Michelle will seek to rally voters in a small number of states that play an outsized role in deciding US presidential elections, known as swing states or battleground states, in the final weeks before the November 5 election.

Arizona, where Obama spoke on Friday, is one such state, with polling averages showing Trump with an average lead of about two points. In Michigan, where Harris spoke on the same day, the Democratic vice president is ahead by less than one point.

Democrats have frequently portrayed Trump as a dangerous and antidemocratic figure, citing his efforts to overturn his loss in the 2020 election based on false claims that the election was “rigged” against him and suggestions that political opponents should face military tribunals.

“Tucson, we do not need to see what an older, loonier Donald Trump looks like with no guardrails,” said Obama.