LOS ANGELES (AP) - Mayor James Hahn began airing his first TV ad of the runoff mayoral campaign Tuesday - a blistering attack on the character and trustworthiness of front-runner Antonio Villaraigosa. The 30-second spot, running on broadcast and cable stations, faults the city councilman for raising thousands of dollars from Florida contributors. Using photographs of newspaper headlines, the ad points out that the county district attorney is reviewing some of those donations. A shot of Villaraigosa appears briefly in the ad, in which he says, "As Mayor, I will lead by example." A narrator responds sarcastically, "The Villaraigosa example...