Parents who muster the willpower to leave their house with an infant know that whatever happens next is wholly unpredictable. That baby might torpedo his or her parent's well-laid plans with multiple diaper blowouts, inexplicable fussing, an insatiable appetite or piercing howls.

So when a parent chooses to attend, of all events, a political rally, trust that supporting their candidate means a lot to that particular mom or dad. In return, politicians generally fawn over babies. If nothing else, a candidate's adoration yields at least one flattering photo from the campaign trail.

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Republican presidential nominee Donald J. Trump knows this political calculus, but managed to single out a mother at a Virginia event on Tuesday by asking that she "get the baby out of here" after it began crying.

Trump boots a baby from his Virginia rally. #MakeDiapersGreatAgain pic.twitter.com/ElwMqL9aYy — Mashable News (@MashableNews) August 2, 2016

While there's debate over whether Trump was joking, his quick pivot from graciousness to sarcasm should give parents pause.

“Don’t worry about that baby. I love babies," he said at first to applause. "I hear that baby crying, I like it. What a baby ... Don’t worry, don’t worry. The mom’s running around like — don’t worry about it, you know. It’s young and beautiful and healthy and that’s what we want.”

Trump showed compassion for a mother trying to calm her child, but his empathy was short-lived. A minute later, Trump could no longer tolerate the baby's cries.

HERE is the full bit of Trump/crying baby: "Actually I was only kidding, you can get the baby out of here." pic.twitter.com/RfD1q9Sonj — Sopan Deb (@SopanDeb) August 2, 2016

“Actually, I was only kidding, you can get the baby out of here," he said. "I think she really believed me that I love having a baby crying while I’m speaking. That’s OK. People don’t understand. That’s OK."

That Trump, or anyone else in the room, would be annoyed by a distressed baby is understandable. Even the most loving parents become irritated by their shrieking children.

It's not yet clear how the mother felt about the exchange with Trump, but when parents brave every conceivable setback to participate in public life with a baby in tow, what they generally hope to receive from strangers is kindness. Parents, who often fear public shaming, hope you realize that it's impossible to prevent or stop every crying fit — and that it's unfeasible to stay home indefinitely because their child might become loud.

Trump poses with a pair of babies during a campaign rally on July 29, 2016, in Colorado Springs, Colo. Image: (AP Photo/Evan Vucci)

These expectations might be too high for ordinary people, but we certainly hope a presidential nominee could either withstand the cries without further comment or find another way to address them. A self-deprecating remark about his own experience as a father, for example, might have signaled his dissatisfaction without risking someone else's humiliation.

But what's most concerning about Trump's treatment of the baby's mother is that he first gave her reason to trust him, but then revoked that confidence to the audience's laughter. And while it might have been a joke, it had the specific purpose of playing the mother for the fool.

Another baby has started crying. A different baby. Will update if Trump tries to have this baby thrown out as well. — Sopan Deb (@SopanDeb) August 2, 2016

The rapid change in Trump's temperament may be unsurprising to some given his recent behavior. He's spent the past few days aggressively criticizing the parents of Capt. Humayun Khan, a Muslim-American soldier killed in Iraq, while alternately calling their son a hero.

Trump's controversial treatment of the Khans is far more newsworthy than his impulsive decision to boot a crying baby from a rally. Yet that single gesture, even if welcomed and condoned by his supporters, provides insight into Trump's arguably erratic behavior. It also does little to assuage concerns that he can treat women with respect instead of turning them into a punch line, as he's done with Heidi Cruz, wife of Republican Sen. Ted Cruz, and Fox News anchor Megyn Kelly, among others.

While the scene at the Virginia rally might have been the perfect comic turn on reality television, where the standard for human decency is depressingly low, it has no place in a presidential campaign. And if Trump can't remain compassionate in the presence of a crying baby and its mother — or Gold Star parents like the Khans — it raises serious questions about who, if anyone, he won’t mock or attack.

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