Luck and a Shrewd Strategy Fueled de Blasio’s Ascension

By MICHAEL BARBARO

Todd Heisler/The New York Times

Bill de Blasio, the New York City public advocate, after he voted in Park Slope, Brooklyn, on Tuesday.

A commercial featuring Bill de Blasio’s son transformed the fortunes of a fourth-place campaign and gave the candidate confidence to attack the mayor and the Police Department’s stop-and-frisk tactic.

• Video Feature: Voter Voices: On the Issues