In an unusual twist, the saga of Mexico City mayor Lopez Obrador has been handled by the Mexican film director Luis Mandoki, who, during 16 years in Hollywood, made eight pictures, including "White Palace," "When a Man Loves a Woman" and "Message in a Bottle." He eventually returned to Mexico, where in 2004 he shot "Innocent Voices." Now Mr. Mandoki is embarking on an as-yet-untitled documentary that will follow Mr. López Obrador through the July 2006 election. Perla Ciuk reports in the New York Times.