IT’S USEFUL that Donald Trump has clarified his plans for Larissa Martinez, who started classes this week as a freshman at Yale University, having graduated in the spring as class valedictorian at her Texas high school. After weeks of waffling, and suggestions that his views on immigration might be “softening,” Mr. Trump has set the record straight: Ms. Martinez has no future in America.

The recipient of a full scholarship to Yale, Ms. Martinez is hoping for a career as a neurosurgeon. As it happens, she’s also a top-notch student, a compelling public speaker and, according to Mr. Trump’s policy, a high priority for deportation.

Discarding his dalliance with fairness and compassion, the Republican presidential nominee this week tossed red meat to the xenophobes in his base by reaffirming his intention to launch a crusade of mass deportations that would target, according to an analysis by The Post, at least 6 million people. Among them, he said, would be immigrants who have overstayed their visas. That category would sweep up Ms. Martinez, who, at age 13, accompanied her mother and sister to the United States on a tourist visa; they stayed after the visa expired, having fled an abusive home in Mexico.

Of course, there is no place in Mr. Trump’s cramped mental universe for someone like Ms. Martinez. To Mr. Trump and the crowds who egg him on, undocumented immigrants are criminals, murderers, rapists, carriers of disease and drug smugglers, fit to be rounded up by deportation agents and shipped far, far away.

Just why Mr. Trump would prioritize visa-overstayers for deportation, and not those who entered the country illegally in the first place, is unexplained. Logic is hardly the point of his policy. He asserts that illegal immigrants have stolen jobs from Americans and triggered a crime wave. In fact, they have met a labor market demand for low-wage workers and been a catalyst for economic growth.

Watch Republican presidential nominee Donald Trump's full speech on immigration in Phoenix. (Victoria Walker/The Washington Post)

While there are undoubtedly instances of terrible crimes committed by unauthorized immigrants — as there are by authorized immigrants, and green card holders, and, it goes without saying, citizens — they are hardly the rule. In fact, young immigrant males are incarcerated at roughly half the rate of native-born Americans. Illegal immigrants, like legal ones, are generally law-abiding and extremely hard-working.

To the GOP nominee, illegal immigrants are a useful instrument with which to whip his supporters into a froth of nativist agitation. He would hire thousands more immigration and Border Patrol agents; he would create a “special deportation task force”; he would round up the criminals whose countries refuse to accept them. He would do it all on Day One, in the first hour, the first minute, in the first fleeting seconds of his administration — by fiat, presumably, because he makes no reference to Congress or legality or judicial precedent. It will all be so fast, so beautiful, so efficient. Believe him.

The self-contained imposter who called briefly on Mexican President Enrique Peña Nieto on Wednesday was masquerading as Donald Trump. In fact, the real Mr. Trump is the man who has been on television all these months, playing on hatred and fear, threatening people such as Ms. Martinez, who represent American values more truly than Mr. Trump ever could.