Trump twice made a slip of the tongue at a Florida rally as he questioned the mental and physical condition of his Democratic rival

Donald Trump insinuated that Hillary Clinton lacks mental stamina at a rally where he twice couldn’t tell what day of the week it was.

“Now, Hillary Clinton, commonly referred to as ‘Crooked Hillary’,” he told a crowd in Kissimmee, Florida. “Hillary Clinton gave a speech today having to do with economic development, having to do with a lot of different things. Short speech, always very short. You know?

“She makes the speech, she turns off the teleprompter. Look, what happens, she gives a short speech then she goes home, goes to sleep, she shows up two days later. Remember, short circuit. Remember that, right? Short circuit.”

Last week the Democratic nominee said that she “may have short-circuited” her answer in a TV interview about the FBI investigation into her use of a private email server as secretary of state. Trump has pounced on the comment. Previously on the campaign trail he has also raised questions over Clinton’s mental and physical condition.

Addressing a rambunctious crowd in Florida, a crucial swing state, he added: “I watched Hillary today, which was really boring. It’s hard to watch. I have an obligation to watch. Fortunately she never goes on very long because she wants to go home.”

But Trump himself, locked in a grueling campaign, twice made a slip of the tongue. “By the way, is there any place to be that’s better than a Friday night in Florida at a Trump rally? No place.”

A few supporters shouted: “It’s Thursday!”

Later he said: “We joke. It’s Friday night and we’re having fun.” More supporters yelled: “It’s Thursday!” but he appeared to assume it was more cheering.

In another, perhaps more deliberate lapse, Trump claimed: “This place is incredible. We’ve got 2,000 people outside trying to get in.” In fact there were still hundreds of empty places in the 8,000-seat arena in Kissimmee, near Orlando.

During the event he launched a series of attacks on Clinton and Barack Obama that were greeted with rowdy cheers and whistles by fans, many wearing Trump regalia and “make America great again” hats.

He held up a series of placards, including one claiming Clinton has received $48.5m in hedge fund contributions. “I received $19,000,” he said. “I don’t even know who it is!” He argued that Clinton would do the bidding of Wall Street.

At another point, he made reference to the US national debt. Trump, whose companies have declared bankruptcy six times according to research by the Politifact website, said: “I’ve always loved debt. I must be honest with you. I don’t love it for countries but I’ve loved it individually. OK? Things work out good, that’s great. If it don’t, you go renegotiate.”

Trump repeated yet again his claim that Obama is the “founder” of Isis, explaining that if the president had maintained a small force in Iraq, he could have prevented the militant group’s rise. He also reiterated his promise to build a wall on the Mexican border, adding: “We’re going to build a wall and, when someone tries to fight us, that wall gets 10ft higher.”

Unfazed by recent poll numbers and negative headlines, Trump described his support as a movement without precedent and insisted: “I’m a messenger for common sense.”

The rally featured crowd chants of “Lock her up!” and the ejection of two protesters. One fan held up a Confederate flag labelled “Trump 2016” but was ordered to remove it before the businessman’s entrance.