WASHINGTON—We might as well start with the mosquito.

Donald Trump was speaking in Cincinnati on Wednesday night, trying to stay something critical about Democrats. But he kept getting distracted by a pest flying around in his line of vision.

“I don’t want mosquitos around me,” he said, whacking on his podium. His voice rose to a shout: “I don’t like mosquitos!” Then he growled, “I don’t like those mosquitos, I never did.” Then, in conclusion, he said, “Speaking of mosquitos, hello Hillary.”

It was one of the most bizarre 15-second sequences you’ll ever see from a presidential nominee. And it wasn’t even the strangest part of the night — which ended with the Republican angrily tweeting a photo of a book of stickers from the Disney film Frozen to mock accusations that he had made an anti-Semitic attack on Democratic nominee Hillary Clinton.

Trump has delivered dozens of unorthodox addresses in a remarkably successful gonzo campaign that has thrilled millions of voters and laid waste to pundit wisdom about how politicians must talk and behave. But his rant Wednesday night was you-gotta-see-it-to-believe-it odd even by his standards.

“Objectively as alarming, in mental-balance terms, as anything we have seen from a major party candidate in modern history,” wrote James Fallows, the Atlantic correspondent and former chief speech writer to President Jimmy Carter.

“A concerned family would be talking about taking car keys away from Donald Trump not giving him nuclear codes,” Stuart Stevens, chief strategist to Mitt Romney’s 2012 campaign and a staunch Trump critic, wrote on Twitter.

“He is absolutely and certifiably insane,” read a post on RedState, a popular conservative website.

The content of the 70-minute speech was bizarre enough. Gifted a fat political pinata to smash — the FBI’s damning Tuesday rebuke of Clinton over her email scandal — Trump instead chased after every mosquito-sized irritant that crossed his mind: NBC host Chuck Todd, media coverage of a recent trip to Scotland, media coverage of his praise of Saddam Hussein, media coverage of his alleged anti-Semitism …

Most striking, though, was Trump’s manner. Frequently shouting, jumping incoherently from topic to topic without finishing sentences, he gave the impression of a man in need of impulse-control counselling, at least a gift certificate to a yoga studio.

How unhinged was he? Clinton urged her followers to watch.

“Newly discovered footage that could destroy Donald Trump’s campaign if everyone saw it,” she tweeted midspeech, sharing a link to the live video feed.

The New York Times, in its straight-news story, called the speech “rambling and sometimes manic-sounding.” Glenn Thrush, Politico’s chief political correspondent, called it “raving.”

The address began as Republican leaders likely wanted it to. Trump, consulting pages of notes, lashed into Clinton for her serial dishonesty on email scandal. But then he threw his papers up in the air, let them land on the floor, and let it rip — in the most self-defeating manner possible.

The email scandal had virtually erased from the news the controversy over a Trump tweet that featured an image of Clinton, a Star of David-like shape, a pile of money and the word “corrupt.”

Trump, though, refused to let his team’s error slide into oblivion. He delivered a prolonged rant defending the star — “It’s a star. Like, a star” — and accusing the people who saw it as a Star of David of being “sick” anti-Semites themselves. Not only that, he said he wished his campaign had not taken the image down.

“Actually, they’re racially profiling,” he said of the media. “They’re profiling, not us. Because why are they bringing this up, why do they bring it up? Because. So anyway.”

By the time he moved on to another topic, he had said the word “star” 28 times.

That would have been sufficient to commence Republican-operative moaning. But Trump, seemingly incapable of letting any criticism slide, also launched into a spirited defence of his controversial and inaccurate Tuesday praise of the late Iraqi dictator Saddam Hussein, who he called “bad” but “good at killing terrorists.”

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“Next day: ‘Donald Trump loves Saddam Hussein.’ I don’t love Saddam Hussein. I hate Saddam Hussein. But he was damn good at killing terrorists,” Trump said Wednesday. “And now terrorists, people that want to be terrorists, they go into Iraq, and I said last night, it’s the Harvard, it’s the Harvard University, it’s the Harvard, of terrorism.”

Trump referred to Todd as “Sleepy Eyes.” He raged about a Clinton attack ad that included an old clip of him golfing. He boasted that he did even better in the Republican primary than the late president and military hero Dwight D. Eisenhower — “who did,” he conceded, “have a lot to do with the victory in the Second World War, in all fairness.”

He stopped talking just after 7:30 p.m. He wasn’t done. Two hours later, he went on Twitter and posted the most unusual campaign rebuttal in memory: a photo, circulated by supporters on Twitter, of a Frozen sticker book with a Star of David-like shape on the cover, under the words “With 50 stickers.”

“Where is the outrage for this Disney book? Is this the ‘Star of David’ also?” Trump wrote. “Dishonest media! #Frozen.”

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