SE Cupp is a CNN political commentator and the host of "SE Cupp Unfiltered." The views expressed in this commentary are solely hers. View more opinion articles on CNN.

At a rally in North Carolina Wednesday night, Donald Trump's supporters broke into a chilling chant when the President invoked the new symbol of his white nationalist campaign for President: Rep. Ilhan Omar.

"Send her back! Send her back!"

Contrary to his claims that he "started speaking very quickly" to silence the chant, the video clearly shows Trump standing back as the chant moved up through the crowd, letting it swell to a crescendo and start to peter out before he began speaking again.

It was a cheap and easy trick -- getting his devotees to turn against a sitting member of Congress in such a vile way, invoking one of the oldest anti-immigrant tropes in American history.

After indulging his supporters in the moment, he is now saying "I disagree with it." Of course, all he has to do is tell them not to say it anymore. We don't have long to wait -- the next rally is scheduled for August 1 in Cincinnati, Ohio.

Never mind that the directive is absurd. Omar is a US citizen and duly elected congresswoman who cannot be "sent" anywhere, except away from public service, should she eventually be unseated.

The "back" that the crowd invoked refers to Somalia, where Omar was born and from where she fled as a refugee, arriving in the US in 1992.

JUST WATCHED Gergen: Trump's actions outdo Nixon in repulsiveness Replay More Videos ... MUST WATCH Gergen: Trump's actions outdo Nixon in repulsiveness 01:27

Why do they want her kicked out of the country? One reason is their flat-out racism. Some probably bristle at the idea of an African refugee serving as an elected representative. Another is politics -- she's been an outspoken critic of American policy, including the US's relationship with Israel, and has, on a number of occasions, made comments that were perceived by some, including me, as anti-Semitic.

Another is merely personal -- that is, relating to Trump's cult of personality. She is his chosen foil at the moment, therefore his followers must revile her the way he does. And in a series of mouth-foaming tweets early this week, the President gave them permission to go -- guns blazing, no holds barred.

It undoubtedly won't be the last time we hear the chant. And its hideousness will likely and unfortunately dull with every use, becoming less and less jarring.

But whatever our eventual indifference to this racist invective, history is a wise judge of character. This will age poorly.

JUST WATCHED Lemon: Will these people chanting be proud in 10 years? Replay More Videos ... MUST WATCH Lemon: Will these people chanting be proud in 10 years? 06:42

As Tim Miller, former Jeb Bush adviser and contributor to The Bulwark, wrote on Twitter: "I'd say to my friends in DC going along with Trump. Imagine how this video of the President leading a white mob in a 'Send Her Back' chant targeting a black refugee is going to look in your kids high school government/history classes. This hatred has got to be stopped."

Chances are, that won't happen soon. Thanks to the many Trump apologists in the Republican Party, Trump has full immunity from the only body that could put an end to his reign of hatred, divisiveness, bigotry and political arson. It will continue, unfettered, until and unless a Democrat can beat him in November of 2020.

Regardless of either party's ability to put an end to Trumpism in the near future, "Send her back" perfectly encapsulates the Trump era, his ambitions and his supporters' zeal for punishing and otherizing his detractors. It covers all the features of the Trump doctrine: an appeal to basest instincts, personal animus, racism, xenophobia, revenge. All packed succinctly into three words.

Much in the way other historical moments have been frozen in a few words or a phrase that tells you everything you need to know about the pervading ideas of the time, "Send her back" will be just as evocative and just as chilling.

What more, for example, do you need to know about the 19th-century pro-slavery argument than Jefferson Davis' famed justification, "If slavery be a sin, it is not yours?" The predicating belief that slavery wasn't only permitted but prescribed by the Holy Scripture is why for so many years American slaveowners could rationalize the practice.

Or President Herbert Hoover's 1930s infamous slogan for the "repatriation" of a million Mexican-American citizens to Mexico: "American Jobs for Real Americans."

The economic fear and paranoia that sparked that mass deportation would be echoed numerous times in our history, including in the 1950s, when President Dwight Eisenhower's hideous "Operation Wetback" went into effect. In a now famous line, Willard Kelly, the assistant commissioner of the border patrol, called the influx of immigrants into the country after World War II "the greatest peacetime invasion ever complacently suffered by any country."

There was the grotesque order from US Col. Karl Bendetsen during the internment of Japanese Americans, to imprison anyone with "one drop of Japanese blood," a call back to the racist classification rule for mixed race children.

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At the height of the Red Scare in the 1950s, Sen. Joseph McCarthy perfectly explained his own "send them back" project with this notable quote: "The reason why we find ourselves in a position of impotency is not because our only powerful potential enemy has sent men to invade our shores ... but rather because of the traitorous actions of those who have been treated so well by this Nation."

Sentiments like these, though they may have been popular at the time, pickled and preserved the rife hatred and bigotry of America's worst, darkest chapters. They tell an awful story of a society vulnerable to malign persuasion and divisive fever dreams, of citizens yielding to fear and loathing and goaded into believing they could avenge their own grievances by punishing others.

"Send her back" may seem easy to shrug off as a cheap rallying cry. But it's so much worse than that. It's the title, in fact, of a new and truly shameful chapter in American politics.