Towering progressive Bill de Blasio almost certainly won New York City’s Democratic primary on Tuesday evening. He trounced previous front-runner Chris Quinn on an unapologetically liberal, anti-Bloomberg platform, following a competent campaign and decades of service in New York City politics. But in reality — the reality defined by Manhattan media, at least — de Blasio won because his son, 16-year-old Dante de Blasio, filmed that touching 15-second political ad you probably saw on YouTube.