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Abandoning a plan to run strictly positive ads in South Carolina, Donald J. Trump’s campaign released one that focused on the 2008 murder of a black teenage athlete in Los Angeles by an illegal immigrant.

The ad features Jamiel Shaw Sr., the teenager’s father, supporting Mr. Trump, who has embraced a hard-line stand against those in the United States illegally and vowed to build a wall along the southern border.

The ad conveys a sense of menace without attacking any of the other Republicans in the race, and highlights a core argument of Mr. Trump’s campaign. It is in some ways evocative of the well-known “Willie Horton” ad that ran against the 1988 Democratic presidential nominee, Gov. Michael Dukakis of Masschusetts. That ad, which featured a black man who killed a white person after being released from prison under a Dukakis administration program, was overtly racial; the Trump ad does not mention the nationality or background of the man convicted in the 2008 killing. The testimonial from the elder Mr. Shaw softens what is otherwise a tough-on-crime, tough-on-illegal-immigration spot. And without a specific attack on another candidate or person, it diffuses a key element of what made the Horton spot famous.

Regardless of how people view the politics of the immigration debate, the spot is certain to stand out amid a clutter of advertising on the South Carolina airwaves.

Mr. Trump has been criticized by Hispanic groups and others since June, when in announcing his candidacy he said of Mexican immigrants: “They’re bringing drugs. They’re bringing crime. They’re rapists. And some, I assume, are good people.”

His stands on illegal immigration, however, have also fueled his popularity; in easily winning the New Hampshire primary, he performed best among voters who said immigration was the issue most important to them, according to exit polls.

Mr. Shaw’s son, Jamiel Jr., 17, known as Jas, was shot dead by an illegal immigrant who, prosecutors said, mistook Jamiel for being a member of an opposing gang because of the color of his backpack. The immigrant, Pedro Espinoza, was convicted and sentenced to death in 2012.

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