A new digital ad campaign from Priorities USA, a “super PAC” supporting Hillary Clinton, equates fighting bigotry with stopping the presidential candidacy of Donald J. Trump. Priorities is spending $500,000 — a large amount for an online ad — on the first commercial, “Dante,” which portrays Mr. Trump as biased against the disabled.

THE AD Flashing “cancer survivor” tattoos on his forearms, Dante Latchman, 17, tells of surviving a rare spinal-cord affliction that was diagnosed when he was 1. “I’ve spent my whole life fighting back,” he says. He is shown watching television and seeing Mr. Trump mock a reporter (Serge Kovaleski of The New York Times) who has a condition that limits the functioning of his joints. “I don’t want a president who makes fun of me, I want a president who inspires me,” Dante says. “That’s not Donald Trump.”

The ad drives home its theme — a “Stop Hate” graphic flips to say “Stop Trump” — as Dante is seen walking down the sidewalk with his mother, his gait noticeably laborious.

THE IMPACT This is the second ad produced by Priorities USA attacking Mr. Trump on this subject, and Mrs. Clinton’s campaign has also seized on Mr. Trump’s mockery of Mr. Kovaleski. What makes this one distinctive and compelling is the ad’s youthful, telegenic protagonist and narrator, who appears to embody both the difficulties that many people with disabilities must confront in their daily lives and the pain that hurtful words can cause. Less a classic attack ad than a scolding one, it takes on added power because of the sympathy that he engenders, much of it wordlessly.