The first frame in the now-famous 33-second ad is taken up almost entirely by Dante de Blasio’s giant Afro.

He was only 15 then, an unlikely star of his father’s equally unlikely victory in the 2013 mayor’s race in New York City.

Through Dante, his father, Bill de Blasio, was able to highlight his biracial family, offer a personal perspective on his policies on affordable housing and early childhood education and signal his intention to end the police practice, known as stop and frisk, that Dante said in the ad “unfairly targets” minorities.

Now, deep into his second and final term as mayor and in the midst of another long-shot candidacy, this time for president, Mr. de Blasio is once again leaning on his son for a boost.