This campaign ad from 1988 is part of the larger politicization of the black underclass. “Willie Horton” and the “welfare queen” both emerged as symbols during this period with which to demonize poor blacks for political clout. Ultimately, using the name Willie Horton became a powerful tool to criticize politicians for being weak on crime and not protecting the innocent white population from the guilty black population.
Ultimately, increasing toughness of the criminal justice system led to a situation, today, where about 1/2 of all black men are in the prison system. See an interesting entry on Willie Horton on wikipedia here.