On the second anniversary of the mass shooting in Tuscon, Ariz., the mother of the massacre's youngest victim is featured in a new ad demanding lawmakers "stand up to the gun lobby." 

"Twenty heartbroken families lost a child in the Sandy Hook school shooting. I know how much it hurts," says Roxanna Green in the ad. Her nine-year-old daughter, Christina-Taylor Green, was killed in Tucson.

"I have one question for our political leaders. When will you find the courage to stand up to the gun lobby?" she asks. "Whose child has to die next?"

The ad comes from Mayor Against Illegal Guns, a coalition formed in 2006 by New York City Mayor Bloomberg (I) and Boston Mayor Thomas Menino (D). 

It will air on cable in Washington through Jan. 14, and in several areas where there have been mass shootings: Tucson; Waco, Texas; Roanoke, Va.; Denver, Colo.; Binghamton, N.Y. and Milwaukee, Wis. In Tucson, the ad will air at or very near 10:10 a.m. local time – when the 2011 shooting took place.

Former congresswoman Gabrielle Giffords, who was seriously wounded in the Tucson shooting has launched a campaign to push for stricter gun laws, saying that the Newton, Conn. massacre spurred her to action.