During a speech on national security in Youngstown, Ohio, Aug. 15, Republican presidential candidate Donald Trump said his Democratic rival Hillary Clinton "lacks the mental and physical stamina to take on" Islamic State militants. Trump frequently suggests Clinton isn't strong enough to be president. (Sarah Parnass/The Washington Post)

During a speech on national security in Youngstown, Ohio, Aug. 15, Republican presidential candidate Donald Trump said his Democratic rival Hillary Clinton "lacks the mental and physical stamina to take on" Islamic State militants. Trump frequently suggests Clinton isn't strong enough to be president. (Sarah Parnass/The Washington Post)

Donald Trump — he who likes to fly home at night in the comfort of his own plane to sleep in the comfort of his own bed — is at it again on the question of Hillary Clinton’s stamina, or alleged lack thereof.

“To defeat crime and radical Islamic terrorism in our country, to win trade in our country, you need tremendous physical and mental strength and stamina,” he said in Wisconsin. “Hillary Clinton doesn’t have that strength and stamina.”

And a day earlier, in case you missed it, “Importantly, she also lacks the mental and physical stamina to take on ISIS, and all the many adversaries we face.”

It’s obvious what’s going on here. The strength-stamina combo is a gender-age twofer, a double whack at Clinton for the price of one. Strength, what men have and women lack; stamina, with its intimations of go-all-night virility. Clinton, in this depiction, is both a weak girl and a dried-up old crone.

No matter that Trump is a year and four months older — and, for that matter, endures a far less rigorous schedule. In Trump World, what counts is the attack, not the truth.

Former Secretary of State Hillary Clinton as she testified before the Senate Foreign Relations Committee in Washington on Jan. 23, 2013. (Saul Loeb/Agence France-Presse via Getty Images)

Trump began hitting Clinton on strength and stamina during the primaries, in a fascinating detour from his usual precision-bombing of opponents. Ordinarily, Trump homes in on an opponent’s actual deficit and proceeds to magnify it: low-energy Jeb, Liddle Marco or, more pertinent at present, Crooked Hillary.

But sometimes, under attack, Trump shifts to that trusty playground tactic — I know you are but what am I? — a move intended to jujitsu the conversation away from his own perceived vulnerabilities. Thus, Trump has trotted out “unstable Hillary Clinton,” “a totally unhinged person” and “like an unbalanced person.” I’m rubber, you’re glue. Whatever you say bounces off me and sticks to you.

Increasingly, though, the rap on Clinton combines gender, age and health in a smarmy package of unsupported insinuation. “She’s a mess, a total mess,” Trump told radio host Hugh Hewitt. “She’ll do an event, she’ll make a short speech off a teleprompter, and then she goes home and goes to sleep.”

When Trump uses the teleprompter, it is a supposed token of maturity and professionalism; when Clinton does, she is failing — indeed, possibly brain-damaged. “She took a short-circuit in the brain,” Trump said in New Hampshire this month, seizing on Clinton’s explanation of how she flubbed an answer on her emails. “Honestly, I don’t think she’s all there.”

Trump is subtle only by comparison with his unhinged allies — and employees. Say-anything, know-nothing spokeswoman Katrina Pierson was on the job Thursday on MSNBC.

“What’s new are the other reports of the observations of Hillary Clinton’s behavior and mannerisms . . . as well as her dysphasia, the fact that she’s fallen, she has had a concussion,” Pierson told Kristen Welker.

“It is extremely important to note that Hillary Clinton has taken a lot of time off the campaign trail,” Pierson added. “It is something that needs to be addressed.”

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What needs to be addressed, actually, is Pierson’s own “behavior and mannerisms,” including her time-traveling assertions that President Obama and Clinton were responsible for the 2004 death of Army Capt. Humayun Khan (“It was under Barack Obama and Hillary Clinton that changed the rules of engagement that probably cost his life”) and alleging that Obama launched the 2001 war in Afghanistan (“Barack Obama went into Afghanistan, creating another problem”).

On the topic of Clinton’s health, Pierson is backstopped by a cabal of conservative websites and commentators who have peddled out-of-context photos and video snippets to paint Clinton as a weakened, stumbling victim of brain damage.

Fox News’s Sean Hannity has been in the repulsive lead, citing video of Clinton’s shaking her head in pretend surprise at being accosted by reporters to suggest neurological injury. “It almost seems seizure-esque to me . . . violent, out-of-control movements on her part,” Hannity said.

Presidential candidates’ fitness for office, including their medical fitness, matters enormously, especially when Trump would be the oldest president ever elected, Clinton second only to Ronald Reagan. Both could reasonably be called on to disclose more health information; the Trumpian claim by the candidate’s physician, that he would be the “healthiest individual ever elected to the presidency,” is particularly risible.

But the Trump & Co. attack on Clinton’s health, with its undertones of ageism and sexism, has no basis in reality, and no place in a presidential campaign. It would be tempting to say this is beneath even Trump, except that it isn’t.

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